How did Christians get from the biblical feast of Passover to Easter sunday?

Here is the biblical answer I've come up with since observant Christians get shy when they realize their favorite time of the year is as uninspired as the Bunny that lays eggs is:

Passover never was changed in the bible, Every one in the Bible who wasn't pagan or heathen kept Passover according to the Law of YHWH God in Exodus 12... Jesus, Moses, the Apostles, the prophets, the king's of Israel, the Corinthians (1Cor 5, 10, 11) and so on. This thing called Easter Sunday or Paschal Sunday, or what ever you want to call it is a man made tradition of some sort. The Bible clearly Tells us of Christ's practice:

Joh 2:23 Now when he was in Jerusalem at the passover, in the feast day, many believed in his name, when they saw the miracles which he did.

Joh 12:1 Then Jesus six days before the passover...

Also it is interesting to note that the ordinance of the bread and wine in memorial if the death of Christ was tied to the Paschal meal and not to Resurrection of Christ as the nominal Sunday practice replicates:

Mat 26:19 And the disciples did as Jesus had appointed them; and they made ready the passover.

Luk 22:15 And he said unto them, With desire I have desired to eat this passover with you before I suffer: 16 For I say unto you, I will not any more eat thereof, until it be fulfilled in the kingdom of God. 17 And he took the cup, and gave thanks, and said, Take this, and divide it among yourselves: 18 For I say unto you, I will not drink of the fruit of the vine, until the kingdom of God shall come. 19 And he took bread, and gave thanks, and brake it, and gave unto them, saying, This is my body which is given for you: this do in remembrance of me. 20 Likewise also the cup after supper, saying, This cup is the new testament in my blood, which is shed for you.

The apostolic tradition of Paul: 1Cor 5:7 Purge out therefore the old leaven, that ye may be a new lump, as ye are unleavened. For even Christ our passover is sacrificed for us: 8 Therefore let us keep the feast, not with old leaven, neither with the leaven of malice and wickedness; but with the unleavened bread of sincerity and truth. 1Cor 11: 23 For I have received of the Lord that which also I delivered unto you, That the Lord Jesus the same night in which he was betrayed took bread: 24 And when he had given thanks, he brake it, and said, Take, eat: this is my body, which is broken for you: this do in remembrance of me. note 25 After the same manner also he took the cup, when he had supped, saying, This cup is the new testament in my blood: this do ye, as oft as ye drink it, in remembrance of me. 26 For as often as ye eat this bread, and drink this cup, ye do shew the Lord's death till he come.

It is obvious that from a Sola Scriptura (Scripture alone) and Tota Scriptura (all of scripture) standing this Easter business needs Reformed and purified.

The only discipes of Jesus who don't keep Passover are Christian's that would rather keep uninspired traditions that never entered in to the mind of God to communicate for his worship.

"Make it clear from scripture based on the bible, where did a prophet or Jesus or his disciples/apostles tell us how to keep this feast we call Easter IN THE BIBLE?"

TL;DR: That's not possible. The Bible doesn't promote Easter, it condemns it.

Passover, and the following Days of Unleavened Bread, is a biblical festival celebrating the ancient Israelites' exodus from Egypt.

In early Chritianity, the festival was celebrated by the Apostles and new Christians with a fuller understanding of its prophetic significance. As Paul said in 1Corinthians 5:7-8,

Purge out therefore the old leaven, that ye may be a new lump, as ye are unleavened. For even Christ our passover is sacrificedIt for us: Therefore let us keep the feast, not with old leaven, neither with the leaven of malice and wickedness; but with the unleavened bread of sincerity and truth.

The Days of Unleavened Bread represent the repentance of a Christian, when they turn from sin and remove it from their lives.

Similarly Passover itself, symbolizes Jesus's sacrifice, he being killed at 3 in the afternoon on the Day of Preparation, at the same time as the lambs were sacrificed for the Passover seder.

Easter is an ancient, pre-Christian festival. The name comes from European mythology according to the Encyclopedia Britanica:

The name Easter, like the names of the days of the week, is a survival from the old Teutonic mythology. According to Bede [an eighth century monk] it is derived from Oestre, or Ostdra, the Anglo-Saxon goddess of spring, to whom the month answering to our April, and called Eoster-monath, was dedicated.

But the myth is ancient, originating with the myth of Semiramus and Nimrod: who had names such as Ishtar and Tammuz in Babylon; Isis and Osiris in Egypt; Astarte and Bel in Syria; Aphrodite, Cybele, or Venus, and Attis or Adonis in Greece and Rome.

Hot-cross buns too have pagan origins according to the Britanica article "bun":

It is quite probable that it has a far older and morIte interesting origin, as is suggested by an inquiry into the origin of hot cross buns. These cakes, which are now solely associated with the Christian Good Friday, are traceable to the remotest period of pagan history. Cakes were offered by ancient Egyptians to their moon goddess; and these had imprinted on them a pair of horns, symbolic of the ox at the sacrifice of which they were offered on the altar, or of the horned moon goddess, the equivalent of Ishtar of the Assyro-Babylonians. The Greeks offered such sacred cakes to Astarte and other divinities. This cake they called bous (ox), in allusion to the ox-symbol marked on it, and from the accusative boun it is suggested that the word 'bun' is derived. Like the Greeks, the Romans eat cross-bread at public sacrifices, such bread being usually purchased at the doors of the temple and taken in with them, a custom alluded to by St. Paul in I Cor. x.28. At Herculaneum two small loaves about 5 in. in diameter, and plainly marked with a cross, were found. In the Old Testament are references made in Jer. vii.18-xliv.19, to such sacred bread being offered to the moon goddess. The cross-bread was eaten by the pagan Saxons in honor of Eoster, their goddess of light. The Mexicans and Peruvians are shown to have had a similar custom. The custom, in fact, was practically universal, ...

We can see references (negative) to this tradition in Jeremiah 7:18:

The children gather wood, and the fathers kindle the fire, and the women knead their dough, to make cakes to the queen of heaven ...

Similarly, both Lent and sunrise services were condemned in Ezekiel 8:14:

Then he brought me to the door of the gate of the LORD's house which was toward the north; and, behold, there sat women weeping for Tammuz.

and 8:16:

And he brought me into the inner court of the LORD's house, and, behold, at the door of the temple of the LORD, between the porch and the altar, were about five and twenty men, with their backs toward the temple of the LORD, and their faces toward the east; and they worshipped the sun toward the east.

Apostolic Christianity continued celebrating Passover for several centuries.

The eastern churches in Jerusalem and Asia Minor held to the Passover tradition. Polycarp, a disciple of John, opposed Rome's position:

Neither could Anicetus persuade Polycarp not to observe what he had always observed with John the disciple of our Lord, and the other apostles with whom he had associated; neither could Polycarp persuade Anicetus to observe it, as he said that he ought to follow the customs of the presbyters that had preceded him.

Polycrates, a disciple and successor of Polycarp, also followed the original faith and wrote:

We ... keep the day scrupulously, without addition or subtraction. All of these [John, Philip, et al.] kept the 14th day of the month ... in accordance with the gospel, not deviating in the least but following the rule of faith. ... I ... am not afraid of threats. Better people than I have said: We must obey God rather than men...

Eventually, Constantine stepped in and Easter was enforced as the official celebration. Those that clung to the biblical holiday were condemned as heretics and Judaizers.

For many centuries after, any individuals or groups noticing that Easter was pagan while Passover was more naturally Christian, were "corrected" by the Roman church. Groups such as the Paulicians, Bogomils, Waldensians, and Cathars were slaughtered by the thousands.

Going from Passover to Easter Sunday is straight-forward. The Passover occurs on the 14^th of Nissan. The next 7-days (the 15^th through the 21^st) are observed by eating Unleavened Bread. During the period of Unleavened Bread, a weekly Sabbath will occur. The day after this weekly Sabbath is the annual Feast of First Fruits:

⁹ And the LORD spoke to Moses, saying, ¹⁰ “Speak to the people of Israel and say to them, When you come into the land that I give you and reap its harvest, you shall bring the sheaf of the firstfruits of your harvest to the priest, ¹¹ and he shall wave the sheaf before the LORD, so that you may be accepted. On the day after the Sabbath the priest shall wave it. ¹² And on the day when you wave the sheaf, you shall offer a male lamb a year old without blemish as a burnt offering to the LORD. ¹³ And the grain offering with it shall be two tenths of an ephah of fine flour mixed with oil, a food offering to the LORD with a pleasing aroma, and the drink offering with it shall be of wine, a fourth of a hin. ¹⁴ And you shall eat neither bread nor grain parched or fresh until this same day, until you have brought the offering of your God: it is a statute forever throughout your generations in all your dwellings. (Leviticus 23) [ESV]

When Jesus rose from the dead, it was the day after the Sabbath, the day of the Feast of First Fruits. Later, when the days of the week were named, the Sabbath became Saturday and the day after the Sabbath became Sunday. Thus, "Easter Sunday" may be seen as a Christian term for the annual Old Testament day of the "Feast of First Fruits."

After the Resurrection, Christianity and Judaism would develop different global systems to set the time for Passover such that they normally do not coincide. Also, the Christian practice of renaming both the days of the week and the period of Passover has focused attention away from the Old Testament Feast of First Fruits. Nevertheless, Christians may rightly point to Leviticus as establishing the day of the Resurrection as an annual day of remembrance.

Now the present day Rabbinic (Jewish) practice of observing First Fruits on a fixed day of the month and differing traditions of observing Passover at a different times of the year, often obscure the connection to Easter Sunday and First Fruits. But occasionally, as is the case this year, they do fall on the same date:

         April
Nissan   2019    Day of Week      Event
14        19     Friday           Passover sacrifice
15        20     Saturday         Sabbath & Unleavened Bread (no work)
16        21     Sunday           First Fruits
17        22     Monday           Unleavened Bread
18        23     Tuesday          Unleavened Bread
19        24     Wednesday        Unleavened Bread
20        25     Thursday         Unleavened Bread
21        26     Friday           Unleavened Bread (no work)
22        27     Saturday         Sabbath

I believe there is a valid issue with the term, Easter Sunday. As Abraham Joshua Heschel observes, throughout history of religion God has been showing His work in redeeming mankind:

One of the most important facts in the history of religion was the transformation of agricultural festivals into commemorations of historical events. The festivals of ancient peoples were intimately linked with nature's seasons. They celebrated what happened in the life of nature in the respective seasons. Thus the value of the festive day was determined by the things nature did or did not bring forth. In Judaism, Passover, originally a spring festival, became a celebration of the exodus from Egypt; the Feast of Weeks, an old harvest festival at the end of the wheat harvest (hag hakazir, Exodus 23:16; 34:22), became the celebration of the day on which the Torah was given at Sinai; the Feast of Booths, an old festival of vintage (hag haasif, Ex. 23:16), commemorates the dwelling of the Israelites in booths during their sojourn in the wilderness (Leviticus 23:42f.). To Israel the unique events of historic time were spiritually more significant than the repetitive processes in the cycle of nature, even though physical sustenance depended on the latter. While deities of other peoples were associated with places or things, the God of Israel was the God of events: the Redeemer from slavery, the Revealer of the Torah, manifesting Himself in events of history rather than in things or places.¹

Using Heschel's observations, prior to the Resurrection of Jesus Christ of Nazareth, the redemptive works of the LORD God look like this:

Agricultural Feast   Old Testament Calendar   Historical Event
Spring festival      Passover                 Judge the gods of Egypt
Spring Festival      Unleavened Bread         Freedom from bondage 
Spring Festival      First Fruits             [Resurrection]
Hag Hakazir          Shavuot                  Giving of the Torah
   ----              Trumpets                      ----
   ----              Day of Atonement              ----
Hag Haasif           Booths                   Being brought to the Promised Land

In the Torah, the LORD God left First Fruits, an agricultural feast, on the calendar. In other words, the transformation of pagan celebrations of nature was not completed. During the time of Unleavened Bread, the nation of Israel must interrupt their remembrance of their release from bondage in Egypt and revert back to celebrating an agricultural event.

Here is my point: a pagan celebration of the spring harvest was changed into a 1-day celebration interrupting the remembrance of being freed from bondage in Egypt. This shows the LORD God had "unfinished" work left on His calendar. The final transformation of the calendar happened on the first "Easter Sunday" when He showed He had freed His people from bondage to death.

So while the Christian practice of an annual celebration of this work of redemption is unquestionably appropriate, calling it Easter Sunday disconnects it from the historical reality it was a day prepared and placed on God's calendar in advance of the actual event. Moreover, by failing to observe it at the same time of the year as Passover, Christians mar God's prophetic use of His calendar as evidence to the Jewish people and to all mankind, that the LORD God of Israel is the one who created the cycles of nature and then chose to redeem His creation using that calendar.

Finally, Christians may rightly ignore the Levitical proscriptions on how First Fruits must be observed when they rightly observe it on Easter Sunday, but we would better serve the LORD God of History if we presented it in the context of the Old Testament record of a God determined to bring His people out of bondage to both sin and death.

1. Abraham Joshua Heschel, The Sabbath, Farrar, Straus and Giroux, 2005, pp. 7-8

One of the great controversies that led to the Schism of 1054 was the type of bread to be used at Passover. For the Roman Catholic, it was unleavened. For the Eastern Orthodox, it was leavened. The symbolism was a contrast of death or life.

As explained here, the Orthodox view meant to observe the resurrection in newness of life, rather than in the oldness of death.

Since Christ, their paschal victim, has been sacrificed, they ought to celebrate the festival not with the old leaven of wicked conduct, but with the unleavened bread of purity and truth.[52] With Christ, they have personally lived the mystery of Easter by dying to sin and rising to a new life.[53] This is why the feast of the resurrection very soon became the priviledged date of baptism, the resurrection of Christians in whom the paschal mystery is relived.

Granted, the argument is a bit of a mixture of metaphor, but the point is for them Passover was an observance of death, rather than life. Hence, observe resurrection, rather than pascha.

PS I am not Eastern Orthodox, so if I have misunderstood, please correct.

>

Easter and Passover are two different celebrations. Passover celebrates the escape of the Israelites from Egypt and the sparing of them from the plague of killing the firstborn. Easter celebrates the much more significant resurrection of Jesus Christ from the dead. You will find these events described in all four of the Gospels in the New Testament, Matthew Mark Luke and John. The resurrection is foreshadowed by Passover and occurred at the same time of year.

Passover is a strictly Jewish celebration and there is no thought that non-Jews would celebrate it. Easter is a celebration for all people that believe in Jesus, whether Jewish or not. Passover celebrations waned as the church became more and more non-Jewish, and an annual Paschal celebration of the Resurrection was well established by the second century AD.

I hope that helps.