Charles Ellicott Commentary Deuteronomy 23:4

"because they met you not with bread and with water in the way, when ye came forth out of Egypt, and because they hired against thee Balaam the son of Beor from Pethor of Mesopotamia, to curse thee." — Deuteronomy 23:4 (ASV)

Because they did not meet you with bread and with water. —We learn incidentally from this passage how the Moabites and the Ammonites requited the forbearance shown them by the Israelites (Deuteronomy 2:9; Deuteronomy 2:19; Deuteronomy 2:29). No one unacquainted with the details of Israel’s interactions with these people on their journey could have written in this way.

Because they hired Balaam against you. —See Numbers 22, Numbers 31:16, and Numbers 25.