The Gospel reading for the 2nd Sunday of Advent in Year A, taken from the Gospel of Matthew, contains a passage I think provides a key to understanding a different and controversial passage from the same Gospel.
When John the Baptist saw the religious leaders coming to be baptized, he challenged them to demonstrate their repentance in concrete actions, not just in playing “show and tell”. He then said to them: “And do not presume to say to yourselves, ‘We have Abraham as our father.'” This criticism is reminiscent of a passage in Jeremiah where he warns the people of Jerusalem: “Do not trust in these deceptive words: ‘This is the temple of the Lord, the temple of the Lord, the temple of the Lord.” (Jer 7:4). Again, being right with God is a matter of making faithfulness concrete, instead of assuming God’s favor based on empty words and practices, or on belonging to the right in-group: ““For if you truly amend your ways and your doings, if you truly execute justice one with another, …then I will let you dwell in this place” (Jer 7:5,7).
John the Baptist further underlines this element of the teaching by declaring: “For I tell you, God can raise up children to Abraham from these stones.” (Mt 3:9). St Paul clarifies this teaching about the true meaning of the Abrahamic heritage at the beginning of chapter 4 of his Letter to the Romans, and again in chapter 3 of his Letter to the Galatians: the true descendants of Abraham are those who are faithful to God.
In the Galatians passage, Paul notes: “that in Christ Jesus the blessing of Abraham might come upon the Gentiles, that we might receive the promise of the Spirit through faith.” (Gal 3:14). This is also the meaning of the somewhat awkward closing passage in today’s 2nd reading, from the latter part of Paul’s Letter to the Romans: “For I say that Christ became a minister of the circumcised/ to show God’s truthfulness,/ to confirm the promises to the patriarchs,/ but so that the Gentiles might glorify God for his mercy./ As it is written: ‘Therefore, I will praise you among the Gentiles/ and sing praises to your name.’ (Rom 15:8-9), a passage which goes on to quote the final verse given in the 1st reading, from Isaiah: “The root of Jesse shall come, raised up to rule the Gentiles; in him shall the Gentiles hope.” (Rom 15:12).
It is this universal character of both salvation and of the true people of God that Jesus is alluding to later on in Matthew’s Gospel when, after criticizing the religious leaders for failing to practice what they preach, He says (among other things): “Call no one on earth your father; you have but one Father in heaven.” (Mt 23:9). This verse, mistranslated in some popular Protestant Bible versions, is often misconstrued to be prohibiting the use of certain words in salutation (the broader passage also mentions “Rabbi” and “Master”, or in some versions “Teacher”). Jesus’ point, however, is simply a call to humility and ecclesial unity, regardless of the terminology: “Whoever exalts himself will be humbled; but whoever humbles himself will be exalted. “(Mt 23:12).
Of all the “Fathers” or “Masters” in history that those Jews might have been tempted to puff themselves up by claiming filial association with, Abraham was the most significant. So when John the Baptist tells the “brood of vipers” not to presume their superior positions by claiming Abraham as their faither, he is calling them to a humility both of faithfulness to God and of a recognition of the universal character of both sinfulness and salvation. We are all brothers, and have one Father, in heaven.