It is a commonplace in New Testament scholarship that Jesus' characteristic address to God as Father was distinctive if not unique in the first century.
According to Scot McKnight, "'Father' occurs only occasionally in the evidence that survives from Second Temple Judaism." Jesus, by contrast, "taught his disciples to pray, as a matter of routine address, 'Our Father'" (McKnight 1999: 54-55; emphasis added).
Richard Bauckham maintains that Jesus' "almost exclusive use of 'Father' to address God was certainly very unusual" and proposes that Jesus' innovation was to adopt "the word 'Father' as his own chosen substitute for the Divine Name." (Bauckham 2020: 53)
Wesley Hill's brief popular exposition of the Sermon on the Mount contrasts Jesus' frequent use of "Father" for God with Old Testament and, by implication, with "[o]ther Jewish texts that ... use 'father' for God":
"T]here remains throughout the Old Testament a certain reserve about the father metaphor for God. ... It is almost as if these rare instances of the God of Israel being called (or calling Himself) 'father' are placeholders, awaiting some unforeseen future revelation that will cause them to take on a new resonance." (Hill 2019: 11 and 106 note 11).
Dale Allison's 1999 attempt at an accessible commentary on the Sermon on the Mount is now rather dated by the get-the-latest-new-book standards of New Testament scholarship, but seems to me to adopt a better approach:
"No prayer in the Hebrew Bible opens with this address, although the idea that God is the father of faithful Israel, his children, is certainly well attested. ... The Mishnah, however, does use the phrase, 'Our Father in heaven' ... and extrabiblical Jewish prayers do have invocations with 'Father.' .... In the light of all the parallels, especially the Qumran texts, it is unwise to insist (as so many have when writing on the Lord's prayer) that Jesus use of 'Abba' was unique. ... At the same time, it remains true that early Christian sources speak of God as Father much more frequently than contemporary Jewish sources; and since Mark 14:36; Rom. 8:15; and Gal. 4:6 transliterate the Aramaic 'abba' into Greek, there is a good chance that the address was thought special because characteristic of Jesus." (Allison 1999: 117)
To be sure, McKnight, Bauckham and Hill are careful enough scholars to avoid referring to Jesus' usage as "unique," but they continue to emphasize discontinuity between Jesus and his Jewish context. Allison explores the same evidence in more detail, and stresses continuity.
I suspect the difference between Allison, on the one hand, and McKnight, Bauckham and Hill, on the other, comes down to scholarly posture:
(1) Allison is more cautious when it comes to filling in historical gaps: As evidence for ancient Jewish references to God as father, Allison quotes from a story in the Bablylonian Talmud about Hanan, the grandson of Honi the Circle Drawer:
"When the world was in need of rain, the rabbis used to send school-children to him who seized the train of his cloak and said to him, Abba, Abba, give us rain! He said to God: Lord of the universe, render a service to those who cannot distinguish between the Abba who gives rain and the Abba who does not." (b.Taanit 23b in Allison 1999:117)
In this case, Allison's caution is warranted. We know far less about Honi the Circle Drawer and his grandson than we do about Jesus. When we crunch the numbers and compare Jesus' usage with that of other ancient Jews, we need to keep the fragmentary nature of our surviving evidence in mind.
(2) Allison actively resists the deeply-ingrained Christian impulse to set Jesus over against his Jewish environment--and for good reason after centuries of Christian denigration of Jews and Judaism. To paraphrase Amy-Jill Levine, we don't need a bad Judaism to have a good Jesus. The authority of Jesus' teaching does not rest on its being unique in all respects. As Allison observes, "A Jew wanting to have nothing to do with Jesus could still pray the Our Father" (1999: 134).
Allison, Dale C. The Sermon on the Mount: Inspiring the Moral Imagination. New York: Crossroad, 1999.
Bauckham, Richard. Who Is God?: Key Moments of Biblical Revelation. Acadia Studies in Bible and Theology. Grand Rapids: Baker Academic, 2020.
Hill, Wesley. The Lord’s Prayer: A Guide to Praying to Our Father. Bellingham, WA: Lexham Press, 2019.
Levine, Amy-Jill. “Bearing False Witness: Common Errors Made about Early Judaism.” Pages 759–63 in The Jewish Annotated New Testament. Edited by Amy-Jill Levine and Marc Zvi Brettler. 2d ed. Oxford: Oxford University Press, 2017.
Levine, Amy-Jill. The Misunderstood Jew: The Church and the Scandal of the Jewish Jesus. San Francisco: HarperSanFrancisco, 2006.
McKnight, Scot. A New Vision for Israel: The Teachings of Jesus in National Context. Grand Rapids: Eerdmans, 1999.