Albert Barnes Commentary Numbers 22:5

"And he sent messengers unto Balaam the son of Beor, to Pethor, which is by the River, to the land of the children of his people, to call him, saying, Behold, there is a people come out from Egypt: behold, they cover the face of the earth, and they abide over against me." — Numbers 22:5 (ASV)

Balaam the son of Beor was from the first a worshipper, to some extent, of the true God, and had learned some elements of pure and true religion in his home in the far East, the cradle of the ancestors of Israel. But though prophesying, doubtless even before the ambassadors of Balak came to him, in the name of the true God, prophecy was still to him, as before, a mere business, not a religion. The summons of Balak proved to be a crisis in his career, and he failed under the trial.

When the gold and honors of Balak seemed to be finally lost, he became reckless and desperate; and, as if in defiance, counseled the evil stratagem by which he hoped to bring about indirectly the ruin of God’s people, which he had been prevented from accomplishing directly. He thus, like Judas and Ahithophel, set in motion a train of events that involved his own destruction.

The name Balaam signifies “destroyer,” or “glutton,” and is in part identical with “Bela, son of Beor,” the first king of Edom (Genesis 36:32). The name “Beor” (“to burn up”) is that of the father, or possibly ancestor, of the prophet.

Pethor, which is by the river of the land of the children of his people — Rather, Pethor which was ... land. Pethor (Pitru, Assyrian) was on the river Sagura (modern: Sajur) near its junction with the Euphrates.