Exodus 34:15

Lest thou make a covenant with the inhabitants of the land ,.... A marriage covenant, taking their daughters in marriage to their sons, and "vice versa", as the following words show; here the caution is to be understood and the words supplied from Exodus 34:12 and inserted and connected thus, "take heed to thyself, lest thou make", &c.;

and they go a whoring after their gods ; that is, the inhabitants of the land, and particularly those with whom the Israelites made a covenant, and entered into a marriage relation with, and perhaps on this condition, that they would abstain from idolatry; and yet, contrary to the obligation they laid themselves under, lust after their idols, and commit spiritual fornication or adultery with them, which is explained by the next clause:

and do sacrifice unto their gods ; such as the first institutors of their idolatry enjoined, and their ancestors had observed, and were according to the rites and customs of the country:

and one call thee, and thou eat of his sacrifice ; invite to eat of what remained, that was offered to the idol: hence it appears, that having feasts at sacrifices, and eating things offered to idols in a festival way, are very ancient practices; see 1 Corinthians 10:27 .