Luz in the Old Testament
Luz was originally the city, Bethel the pillar and altar of Jacob; in Gen. 12:8 it is called Bethel by anticipation (Gen. 28:19), after Ephraim's conquest the town Bethel arose. The nearness of the two accounts for their being identified in all cases where there was no special reason for distinguishing them. After one of the townsmen of ancient Luz had betrayed it to Israel he went into "the land of the Hittites," and built a city of the same name (Judg. 1:23-26).
International Standard Bible Encyclopedia, which is in the public domain (with minor edits).