Your first father sinned, And your mediators have transgressed against Me. Therefore I will profane the princes of the sanctuary; I will give Jacob to the curse, And Israel to reproaches. (Isaiah 43:27-28)
What is the meaning of "your first father" here? Does it refer to Adam and the original sin? Or does it refer to the founder of "Jacob/Israel" as a nation? If so which of the founders is meant?
Commentators give widely varying answers:
Cambridge Bible for Schools and Colleges: Undoubtedly Jacob, the eponymous hero of the nation, is meant (cf. Hosea 12:3 f.), not Abraham (who is never spoken of in the later literature as sinful), nor the earliest ancestors collectively; still less Adam.
Pulpit Commentary: Even thy first father, Abraham, sinned (Genesis 12:13, 18; Genesis 17:17; Genesis 20:2); and thy teachers have transgressed.
Benson: Some think that Urijah, who was high-priest in the time of Ahaz, is here especially meant: see 2 Kings 16:10-11. But it is more probable that the expression is put for their forefathers collectively; and so he tells them, that as they were sinners, so also were all their progenitors, yea, even the best of them.
Ellicott: The words have been interpreted: (1) of Adam; (2) of Abraham; (3) of Jacob; (4) of the ancestors of Israel collectively; (5) of this or that high priest individually. (3) fits in best.
I would add one more possibility. In the quote, "Jacob" is contrasted with "Israel." In that sense, "Jacob" means the nation of Judah and "Israel" means the northern tribes. [note: this argument is incorrect. See below.] In that case the most likely candidate for the "first father" would be either David or Solomon, the kings who ruled before the nation divided. David's sins were mostly personal and not disqualifying to the nation. Solomon, however, committed the sin of supporting idolatry, the very sin which the Bible says resulted in the destruction of both Judah and Israel as independent nations. So if the quote refers to Jacob and Israel as nations, Solomon is the most likely culprit.
The question again: Who is "your first father" in Isaiah 43:27?
Note: I need to withdraw the argument that Isaiah contrasts Jacob and Israel. In fact he consistently uses them as synonyms. My suggestion of Solomon as the culprit here is still worthy of consideration however.