Genesis 12:8

And he removed from thence unto a mountain on the east of Bethel, and pitched his tent, having Bethel on the west, and Hai on the east: and there he builded an altar unto the LORD, and called upon the name of the LORD.

And he removed from thence unto a mountain - Hebrew, the mountain.

Pitched his tent, having Beth-el on the west, and Hai on the east - "Beth-el," then called Luz (now Beitin). "Hai," properly "Ai" [Hebrew, haa-`Ay (H5857), always with the definite article, and hence, contracted into Hai]. 'The distance between Bethel and Hai,' says Porter ('Handbook, Syria') 'is three-fourths of an hour's ride. The road passes over a ridge, on the top of which is a level plateau, stony, but still fertile, when compared with the rocky wilderness around.' It was on this spot, between Beth-el and Hai, a day's journey south from Shechem, that Abram encamped and built an altar.'

Builded an altar. By this solemn act of devotion he made an open profession of his religion, established the worship of the true God, and declared his faith in the promise.