Thus says the LORD: “For three transgressions of the Ammonites, and for four, I will not revoke the punishment, because they have ripped open pregnant women in Gilead, that they might enlarge their border.
He now prophesies against the Ammonites, who also derived their origin from the same common stock; for they were the posterity of Lot, as it is well known; and Lot was counted as the son of Abraham, as Abraham, having taken him with him from his country brought him up, no doubt, as his own son. Then Abraham was the common father of the Jews and of the Ammonites.
What the Lord says here may be explained by what he says Jer 12:14, Thus said the Lord, against all my evil neighbours that touch the inheritance of my people Israel, Behold, I will pluck them out. Damascus was a near neighbour to Israel on the north, Tyre and Gaza on the west, Edom on the south, Ammon and (in the next chapter) Moab on...
Commenting on Amos 1:3-15
Thus saith the Lord, for three transgressions of the children of Ammon,.... These are the descendants of Benammi, a son of Lots, by one of his daughters, Gen 19:38; are distinguished from the Ammonites, Ch2 20:1; were near neighbours of the Jews, but great enemies to them, though akin: and for four, I will not turn away the punishment thereof; See Gill on Amo 1:3.