What evidence is there that God as father was a common concept for Jesus's first century Jewish audience?

The revelation of the New Testament vastly exceeds anything that preceded it : especially so in regard to the fatherhood of the Father.

So I can find no evidence at all in the pages of the bible that what was revealed in the gospel was already familiar to the generality of Jewish belief at the time of Jesus' ministry.

The coming of the Son of God is that which reveals the true nature of God and which reveals the fatherhood of God, the Father.

Until that time, yes, God was a 'father' to Israel but Israel constantly rejected the Deity as can readily be seen in the history of that nation ; in the journey through the wilderness ; in the time of the Judges ; in the time of Saul ; of David and of the following kings of both Israel and Judah.

Thus, the rejection of Deity by the seed of Adam (exampled by that most privileged of all of that seed, Israel) showed the necessity of another kind of humanity to fulfil the purposes of God.

And that is seen, only, in the coming of the Son of God.

That which was 'the life, the eternal', 1 John 1:2, 'was manifested'. He who was the logos (and God was the logos, John 1:2) was, in the beginning, with God, John 1:1, and 'became flesh', John 1:14.

Thus the revelation of the Son.

And this revelation reveals the Father. The Father who begets the Son. For God does not 'create' the Son, He begets the Son. The Son is begotten of the Father not fashioned out of other substance.

This astounding revelation heralds the New Testament and the New Creation : a testament of redemption out of Adam and into Christ by a New Creation that is of Spirit. A union of Spirit (that is to say a union of Holy Spirit and the spirit of man) that brings in a new humanity.

This humanity is under the Headship of Jesus Christ : He, the Head, they the Body. These things are revealed in the gospels, the epistles and the book of Revelation.

This revelation is far, far greater than anything which preceded.

As far as the heavens are above the earth, so far does this revelation exceed what little was able to be known among the natural seed of Abraham : Israel.

There are prophetic hints, indeed and of course, as there are prophetic hints of the Messiah himself, Jesus Christ, and hints of his redemption, of justification, of the Body of Christ and what it will entail, but they are faint wisps of imagery and metaphor compared to the staggering revelation when, ultimately, the Father sent the Son to be the Saviour of the world.

The four evangelists, Matthew, Mark, Luke and John, clearly document that the Jews, as a nation, had thoroughly rejected these hints and nuances scattered throughout the Hebrew scriptures by the prophets. Thus Jesus constantly had to rebuke those around him, for unbelief, and had to repeatedly, in his ministering, warn his hearers of the Pharisees, of the Sadducees, of the Doctors of the Law and of the scribes that neither their way nor their ideology were any part of the New Testament.

I'm surprised no one mentioned Jeremiah 3:19.

“I myself said,

“‘How gladly would I treat you like my children and give you a pleasant land, the most beautiful inheritance of any nation.’ I thought you would call me ‘Father’ and not turn away from following me.

This is a very relational statement of God as Father, more than just progenitor. I agree with others that have pointed out that people who heard Jesus use the term Father did not stumble over the term itself, how ever much they might have objected to how he used it.

So while the concept was not new, Jesus' persistent use of it was. It was revelational since no one previously had given the fatherhood of God the kind of daily, intimate relationship that Jesus emphasized. Mattew 5-7 outlines in detail how intimately bound our faith-walk is with God as Father. There is no parallel in the Old Testament.

How does God amplify a message? How does the Almighty drive his point home? Here are some ways:

1. Repetition
2. Miracles
3. First Position
4. Middle Position
5. Last Position

Repetition: The Old Testament makes many references to God as Father.

Miracles. The defining miracle for the existence of a special people possessed by God was Abram's transformation into Abraham through the miraculous birth of a child. He went from exalted father to father of many nations. Typologically, Abraham represents God as a Father.

First Position. The story of Abraham is a pivotal event in the first book of the Bible, Genesis. Or if you accept that Job may have been written first, that man is presented as a loving father, and God's speech is infused with a Father's care for his creation.

Middle Position. The central and longest book is Psalms. God as Father and as protector of the fatherless, as well as in analogous references appears in Psalms 2, 3, 20, 68, 77, 82, 89 and 103 (and possibly others I overlooked). The Bible is filled with chiasms which put the central idea at the middle of a structure, thus putting a main point in Psalms is natural.

Last Position. When someone delivers a message, the last thing they say carries special weight. The last prophet to speak in Israel was Malachi. This is what he said:

“A son honors his father, and a slave his master. If I am a father, where is the honor due me? If I am a master, where is the respect due me?” says the Lord Almighty. “ (Malachi 1:6)

Do we not all have one Father? Did not one God create us? Why do we profane the covenant of our ancestors by being unfaithful to one another? (Malachi 2:10)

“So I will come to put you on trial. I will be quick to testify against sorcerers, adulterers and perjurers, against those who defraud laborers of their wages, who oppress the widows and the fatherless, and deprive the foreigners among you of justice, but do not fear me,” says the Lord Almighty. (Malachi 3:5)

“On the day when I act,” says the Lord Almighty, “they will be my treasured possession. I will spare them, just as a father has compassion and spares his son who serves him. (Malachi 3:17)

Thus by many common measures of deducing the importance of a concept or the central message of a document, the idea of God as Father is of great importance in the Old Testament. There is one other, alluded to by Malachi:

Honor your father and your mother.

By placing this at the heart of the Ten Commandments, at the heart of the Law, God made sure to emphasize this relationship.

Sadly, the judgment of Malachi suggests that all the pains that the Lord took to drive that point home were lost on them. Their sacred writings were full of this analogy, but many in Israel did not regard God as a father except in a formal, religious sense. In their heart, the idea was foreign to them.

The Old Testament identifies YHWH as "our Father", the Creator.

Malachi 2:10

Have we not all one Father? Has not one God created us? Why do we deal treacherously with one another By profaning the covenant of the fathers?

Isaiah 64:8

But now, O YHWH, You are our Father; We are the clay, and You our potter; And all we are the work of Your hand.

Isaiah 63:16

Doubtless You are our Father, Though Abraham was ignorant of us, And Israel does not acknowledge us. You, O YHWH, are our Father; Our Redeemer from Everlasting is Your name.

Deuteronomy 32:6

Do you thus deal with YHWH, O foolish and unwise people? Is He not your Father, who bought you? Has He not made you and established you?

John 8:41

Then they said to Him, “We were not born of fornication; we have one Father—God.”

Jesus declares his Father to be the same God as the Jews, YHWH.

John 8:54

Jesus answered, “If I honor Myself, My honor is nothing. It is My Father who honors Me, of whom you say that He is your God."

Paul appears to feel the same way.

2 Timothy 1:3

I thank God, whom I serve with a pure conscience, as my forefathers did, as without ceasing I remember you in my prayers night and day,

Ephesians 4:6

one God and Father of all, who is above all, and through all, and in you all.

Deuteronomy 32:6 Do you thus repay the LORD, you foolish and senseless people? Is not he your father, who created you, who made you and established you?

Isaiah 45:11 Thus says the LORD, the Holy One of Israel, and the one who formed him: “Ask me of things to come; will you command me concerning my children and the work of my hands?

Isaiah 63:16 For You are our Father, though Abraham does not know us And Israel does not recognize us. You, LORD, are our Father, Our Redeemer from ancient times is Your name.

God clearly implies His fatherhood over Israel in the context of His covenantal creatorship of them.

Was Jesus teaching of God as our Father already well known to his Jewish audience?

Yes, they would be very familiar with the reality of His role as their heavenly Father, Yahweh, their Lord and God. Based on this sampling, Jesus was not introducing a new concept of God as Father.

The concept of God as Father to the nation of Israel was not new when Jesus spoke of that in, for example, Matthew 6:9 where he instructed prayer to God to be addressed, "Our Father who is in heaven..." His audience then were Jewish people. Nobody seemed to express surprise, or dismay, or puzzlement. To address God as "Father" was the instruction of the Son.

There are various scriptures in the Old Testament that present the concept of God as Father in a symbolic, national way. Nor was it always "at a distance", purely as a manner of speaking; God told David regarding the time after his death when Solomon would build the temple, "I will be his father, and he shall be my son." (2 Samuel 7:14) Such an intimate, personal oversight of God with Solomon must have been a great comfort to David, and the whole nation would likely know of that paternal promise.

However, the number of times God speaks of himself as a Father to Israel are not frequent. The religious leaders, scribes and prophets would be familiar with the concept in scripture, but how could we ascertain whether the nation, as a whole, grasped the significance of this? Indeed, even those leaders showed they failed to appreciate this close relationship God would have, even with believing individuals, when they had dealings with Jesus of Nazareth.

The way he spoke of God as Father offended them. This shows they did not understand the prophecy in Isaiah about a future son (who they refused to identify as Jesus):

"For unto us a child is born, unto us a son is given: and the government shall be upon his shoulder: and his name shall be called Wonderful Counsellor, The mighty God, The everlasting Father, the Prince of Peace." (Isaiah 9:6 Emphasis mine)

Therefore, when Jesus spoke of God as his Father, they spitefully disrespected both the Father and the Son by telling Jesus they were not children of adultery (showing their view of Jesus being illegitimate) claiming instead that they had God as their Father. That was when Jesus bluntly told them that their father was the Devil, not God, and they did the deeds of their real spiritual father. (John 8:38-45)

This suggests that the religious leaders, the scribes and those well studied in the scriptures would already have noted the concept of God as Father, but not enough to understand its application. If it was really only a figure of speech to them, denoting spiritual legitimacy and inheritance, that would account for the way they disrespected Jesus calling God his Father. They viewed Jesus as a false Messiah who would not be recognised by God as one of his, as were they. The concept of being able to boast in a superior spiritual, divine legitimacy and inheritance was very familiar to them. That is why Jesus rebuked them so.

Jesus came to show the fatherhood of God in his own person, being the everlasting Father of Isaiah 9:6. Those who longed to know God as Father were attracted to Christ, the Son. They would not understand at first how it worked out; only that there was something about this man, Jesus, that drew them to God as Father. On the other hand, those who were full of pride in their spiritual Father being God showed their concept to be as common as muck; earthy, not spiritual; promoting their person, not graciously showing God's close personal relationship with the humble and meek.

This means it's not how common the concept was that matters - it's whether their concept was correct, or twisted. Jesus the Son exposed that by the way he kept calling God his Father, in an astonishingly intimate, personal way. No Israelite ever dared to speak of God as Father in such a way. Jesus came to lead the humble to God as Father in a new, profound way, if they came to him as the Son (John 14:6 & 23).

This means that the answer to your last question is that Jesus' teaching was a major new revelation of God's nature because he came to personally reveal it as only the Son could do, which the scriptures could only indicate obliquely.