Pethor
Pethor is a city in Mesopotamia, on the Euphrates, fixed in scripture as the home from which Balak of Moab summoned Balaam to curse Israel.
The dispatch from Moab
Balak's messengers go to Pethor to fetch the seer: "And he sent messengers to Balaam the son of Beor, to Pethor, which is by the River, to the land of the sons of Amav, to call him, saying, Look, there is a people come out from Egypt: see, they cover the face of the earth, and they dwell across from me" (Nu 22:5). The locator "by the River" places Pethor on the Euphrates; "the land of the sons of Amav" gives its regional setting.
Remembered in the assembly law
When Deuteronomy bars Ammon and Moab from the assembly of Yahweh, it grounds the exclusion partly on the Pethor errand: "because they did not meet you⁺ with bread and with water in the way, when you⁺ came forth out of Egypt, and because they hired against you Balaam the son of Beor from Pethor of Mesopotamia, to curse you" (De 23:4). The two notices together fix Pethor as the geographical anchor of the Balaam episode — far enough away to require messengers, identifiable enough to be named twice.