Ai in the Old Testament
Ai (Gen. 12:8) was a royal city (Josh. 7:2; 8:9,23,29; 10:1,2; 12:9); E. of Bethel, "beside Bethaven." The second Canaanite city taken by Israel and "utterly destroyed." The name AIATH still belonged to the locality when Sennacherib marched against Jerusalem (Isa. 10:28). "Men of Bethel and Ai," (223 according to Ezra 2:28, but 123 according to Neh. 7:32,) returned from Babylon with Zerubbabel.
Ezra's list was made in Babylon; Nehemiah's in Judaea long after. Death and change of purpose would make many in Ezra's list of intending returners not appear in Nehemiah's list of those actually arriving. Aija is mentioned among the towns reoccupied by the Benjamites (Neh. 11:31). Perhaps the site is at the head of Wary Harith. See BETHEL.
There is a hilltop E. of the church remains on the hill adjoining and E. of Bethel (Beitin); its Arab name, et Tel, means "the heap," and it doubtless is the site of Ai, or Hai (on the east of Abraham's encampment and altar, Gen. 12:8). In the valley behind Joshua placed his ambush. Across the intervening valley is the spot where Joshua stood when giving the preconcerted signal.
The plain or ridge can be seen down which the men of Ai rushed after the retreating Israelites, so that the men in ambush rose and captured the city behind the pursuers, and made it. "a heap" or tel for ever. 2. A city of Ammon, near Heshbon (Jer. 49:3).
International Standard Bible Encyclopedia, which is in the public domain (with minor edits).