How did the Christian movement distinguish itself from Judaism?

Christianity distinguished itself from Rabbinic Judaism by maintaining a priesthood, an altar, and a sacrifice commemorating (i.e. making present) Jesus' sacrifice each time the Divine Liturgy was celebrated. (See the prayers in the Divine Liturgy of St. James, of St. John Chrysostom, and of St. Basil). After the Temple was destroyed, Judaism kept none of those things either literally or symbolically.

See the Epistle to the Hebrews by St. Paul (first century, included in the New Testament), 'The Dialogue with Trypho' by Justin Martyr (second century), and the Epistle of Barnabas (second century) for more information.

Christianity distinguished itself from Rabbinic Judaism in believing that Jesus is messiah, and in particular a lawgiver "greater than Moses" and therefore with the authority to change the Laws of Moses. That sort of thinking undermines Judaism, and therefore is unthinkable to Jews of any time.

Within the time period covered by the New Testament itself, and extending forward from that period historically, Christianity set itself apart from Judaism in two primary ways:

1. Accepting Jesus Christ as the promised Messiah, a claim that was and still is explicitly rejected by the main body of Judaism.
2. Rejecting observance of the Torah or Law of Moses as binding upon Christians.

Accepting Christ as the promised Messiah

This took place within the lifetime of Jesus, as recorded in the Gospels. Establishing this belief is one of the primary purposes of the Gospels--especially the Gospel of Matthew, which opens with these words:

This is the genealogy of Jesus the Messiah the son of David, the son of Abraham. (Matthew 1:1, NIV)

This verse is more commonly translated as "the genealogy of Jesus Christ . . . ." However, the Greek word Χριστός (Christos) is used as a translation of the Hebrew word מָשִׁיחַ (mashiyach). Both of them mean "anointed," i.e. anointed as a king or priest, but usually used of an anointed king. Wherever we read "Christ" in English Bibles, it is designating Jesus as the Messiah, or Anointed One.

In addition to consistently referring to Jesus as the Christ, or Messiah, the Gospels also contain explicit statements of his position as the Messiah. For example:

"But what about you?" he asked. "Who do you say I am?"

Simon Peter answered, "You are the Messiah, the Son of the living God."

Jesus replied, "Blessed are you, Simon son of Jonah, for this was not revealed to you by flesh and blood, but by my Father in heaven." (Matthew 16:15-17)

In addition, by making the Messiah "the Son of God," and divine, the early followers of Christ violated Jewish teachings about the nature of God:

For this reason they tried all the more to kill him; not only was he breaking the Sabbath, but he was even calling God his own Father, making himself equal with God. (John 5:18)

"We are not stoning you for any good work," they replied, "but for blasphemy, because you, a mere man, claim to be God." (John 10:33)

This became the primary issue at Jesus' trial in front of the Sanhedrin:

The high priest said to him, "I charge you under oath by the living God: Tell us if you are the Messiah, the Son of God." (Matthew 26:63)

When Jesus answered in the affirmative (using a common locution meaning "yes"), the Sanhedrin sentenced him to death for blasphemy.

In this encounter, as in others, the Jewish authorities explicitly rejected the claim of Jesus and his disciples that he was the Messiah. This remains the position of Judaism to this day (aside from Messianic Jews, who are not considered Jews by the main bodies of Judaism).

According to the Gospel narratives, even within Gospel times themselves the Jewish leaders excluded from the synagogue, and by implication declared non-Jewish, anyone who accepted Jesus as the Messiah:

The Jewish leaders . . . already had decided that anyone who acknowledged that Jesus was the Messiah would be put out of the synagogue. (John 9:22)

The belief that Jesus was the Christ, or Messiah, then, was the key point on which followers of Christ, or Christians, distinguished themselves from Judaism, and the key point on which Judaism originally rejected Christianity as Jewish.

Rejecting observance of the Torah or Law of Moses

Jesus did not explicitly require his followers to reject the ritual Law of Moses. In some cases, he even instructed people to observe those rituals. For example, after healing a man of leprosy, Jesus commanded him:

"See that you don’t tell anyone. But go, show yourself to the priest and offer the gift Moses commanded, as a testimony to them." (Matthew 8:4)

However, on a number of occasions Jesus incurred the wrath of the Jewish leaders by violating their ritual laws. Here is one well-known example:

Going on from that place, he went into their synagogue, and a man with a shriveled hand was there. Looking for a reason to bring charges against Jesus, they asked him, "Is it lawful to heal on the Sabbath?"

He said to them, "If any of you has a sheep and it falls into a pit on the Sabbath, will you not take hold of it and lift it out? How much more valuable is a person than a sheep! Therefore it is lawful to do good on the Sabbath."

Then he said to the man, "Stretch out your hand." So he stretched it out and it was completely restored, just as sound as the other. But the Pharisees went out and plotted how they might kill Jesus. (Matthew 12:9-14)

It could be quibbled that there was not an explicit law in the Torah, or Law of Moses, forbidding healing on the Sabbath. However, Jesus did explicitly nullify various commandments that were clearly stated in the Torah. For example:

"You have heard that it was said, 'Eye for eye, and tooth for tooth.' But I tell you, do not resist an evil person." (Matthew 5:38-39)

This nullified a law given not once, but at least three times in the Torah:

But if there is serious injury, you are to take life for life, eye for eye, tooth for tooth, hand for hand, foot for foot, burn for burn, wound for wound, bruise for bruise. (Exodus 21:23-35)

Anyone who injures their neighbor is to be injured in the same manner: fracture for fracture, eye for eye, tooth for tooth. The one who has inflicted the injury must suffer the same injury. (Leviticus 24:19-20)

The judges must make a thorough investigation, and if the witness proves to be a liar, giving false testimony against a fellow Israelite, then do to the false witness as that witness intended to do to the other party. You must purge the evil from among you. The rest of the people will hear of this and be afraid, and never again will such an evil thing be done among you. Show no pity: life for life, eye for eye, tooth for tooth, hand for hand, foot for foot. (Deuteronomy 19:18-21)

And Jesus was very explicit about rejecting a law embodied in the Mosaic Law in his response to a question about divorce:

Jesus replied, "Moses permitted you to divorce your wives because your hearts were hard. But it was not this way from the beginning." (Matthew 19:8)

After Jesus' death, the issue of whether Christians must observe the Law of Moses became a full-blown debate among the early Christian Apostles and believers.

The Jewish-born Christians in Jerusalem, traditionally believed to be led by James, the brother of Jesus, held that the body of followers of Christ must observe Jewish law.

But the Apostles who were evangelizing among the gentiles, notably Paul, Barnabas, and Peter, argued that Christ had fulfilled the Law, and that Christ had sent them to spread the Gospel to the gentiles, and that therefore observance of the ritual laws and behavioral codes of the Torah, or Law, was not necessary for Christians. (See also Peter's vision of a sheet containing all kinds of animals in Acts 10:9-23)

This is the real force, in its historical context, of Paul's statement:

We maintain that a person is justified by faith apart from the works of the law. (Romans 3:28)

In Paul's letters (as in the Septuagint, which Paul relied upon heavily), the Greek word νόμος (nomos), "law," is commonly used as a translation of the Hebrew word תּוֹרָה (towrah), "Torah, Law," referring to the Law of Moses as set out in the first five books of the Hebrew Bible: Genesis through Deuteronomy. In most cases, it should be capitalized in translation as "Law" in order to indicate this meaning.

That is why, in Paul's discussions of being saved by faith apart from the works of the Law, he commonly refers to "circumcision"--as he does in the verses following that oft-quoted statement in Romans 3:28:

Or is God the God of Jews only? Is he not the God of Gentiles too? Yes, of Gentiles too, since there is only one God, who will justify the circumcised by faith and the uncircumcised through that same faith. Do we, then, nullify the law by this faith? Not at all! Rather, we uphold the law. (Romans 3:29-31)

The whole of Romans 3, and the Epistle to the Romans generally, is an extended argument in the debate with the Jerusalem Christians over whether followers of Christ must observe the Jewish law. That law was commonly referred to as "circumcision," since being circumcised was (and still is) the physical sign and symbol that a person was (and is) an observant Jew.

This debate led to a meeting recounted in Acts 15:1-35, which church historians have dubbed the "Council of Jerusalem," believed to have taken place around 50 AD. Here was the issue under dispute, as related at the beginning of its narrative account in Acts 15:

Certain people came down from Judea to Antioch and were teaching the believers: "Unless you are circumcised, according to the custom taught by Moses, you cannot be saved." This brought Paul and Barnabas into sharp dispute and debate with them. So Paul and Barnabas were appointed, along with some other believers, to go up to Jerusalem to see the apostles and elders about this question. (Acts 15:1-2)

And the issue is stated again in verse 5:

Then some of the believers who belonged to the party of the Pharisees stood up and said, "The Gentiles must be circumcised and required to keep the law of Moses." (Acts 15:5)

From the ensuing debate, the following decision emerged and was promulgated to the non-Jewish believers:

Therefore we are sending Judas and Silas to confirm by word of mouth what we are writing. It seemed good to the Holy Spirit and to us not to burden you with anything beyond the following requirements: You are to abstain from food sacrificed to idols, from blood, from the meat of strangled animals and from sexual immorality. You will do well to avoid these things. (Acts 15:27-29)

This established definitively that Christians would not be required to be circumcised and observe all of the ritual and behavioral codes of the Torah, though a few prohibitions made in the Mosaic Law were still enjoined upon believers as things they would "do well to avoid."

Since that time, it has been the accepted belief and practice of nearly all Christian denominations and sects that it is not necessary for Christians to observe the ritual and behavioral codes enjoined in the Torah, or Law of Moses.

This became a second fundamental division between Christianity and Judaism.

Judaism as a religion is defined primarily by its observance of the Torah or Law of Moses, and of the body of rabbinical law that has grown up around the Law of Moses.

By declaring that Christians need not observe the Law of Moses and the accompanying rabbinical laws that are binding upon Jews, the early Apostles, and following them Christianity as a whole, decisively split from Judaism and became a whole new religion rather than a sect of Judaism.

How did Christian movement distinguish itself from Judaism?

Early Christians did not try to distinguish themselves as a movement. They had hopes that the rest of the Jews would accept Jesus as their Savior. Such attempts at "branding" are more consistent with modern marketing techniques.

The early church was entirely made up of Jews. They were sort of under siege in Jerusalem. Jewish leaders had declared a type of excommunication for anyone following Jesus that probably included economic sanctions.

John 9:22 These words spake his parents, because they feared the Jews: for the Jews had agreed already, that if any man did confess that he was Christ, he should be put out of the synagogue.

Acts 2:44-45 And all that believed were together, and had all things common; And sold their possessions and goods, and parted them to all men, as every man had need.

The sanctions against Christians did not end and eventually other Christians had to sent money to support the Christians in Jerusalem.

1 Corinthians 16:1-3 Now concerning the collection for the saints, as I have given order to the churches of Galatia, even so do ye. Upon the first day of the week let every one of you lay by him in store, as God hath prospered him, that there be no gatherings when I come. And when I come, whomsoever ye shall approve by your letters, them will I send to bring your liberality unto Jerusalem.

When Paul (who was an apostle to the gentiles) first came to a new town, he would preach to the Jews first.

Acts 13:41-42 Behold, ye despisers, and wonder, and perish: for I work a work in your days, a work which ye shall in no wise believe, though a man declare it unto you. And when the Jews were gone out of the synagogue, the Gentiles besought that these words might be preached to them the next sabbath.

Christianity spread in the early church because the Father drew men to respond to Jesus.

John 6:44 No man can come to me, except the Father which hath sent me draw him: and I will raise him up at the last day.

The core of Judaism is the law and the law was not in opposition to Christianity, it was a stepping stone.

Galatians 3:24 Wherefore the law was our schoolmaster to bring us unto Christ, that we might be justified by faith.

For the first 100 years most people saw Christianity as a sect of Judaism. Both Judaism and Christianity were sporadically persecuted until around 300 AD. Christianity grew as it did because the Father drew people to Jesus. In the next 100 years what was called Christianity became a mixture of political and religious organizational systems which claimed authority over anyone calling themselves Christian.

Once Christianity was mixed with political and religious systems, coercive force was made available. Those who wielded such force could make Christianity distinguishable by killing anyone who resisted being called a Christian.

Even to this day it is difficult to distinguish between Biblical Christianity and organizational or systems Christianity. When Christianity was in social favor, many people would claim to be Christian. As Christianity falls into social disfavor, it will become a much smaller group.