Charles Ellicott Commentary Exodus 34:15-16

"lest thou make a covenant with the inhabitants of the land, and they play the harlot after their gods, and sacrifice unto their gods, and one call thee and thou eat of his sacrifice; and thou take of their daughters unto thy sons, and their daughters play the harlot after their gods, and make thy sons play the harlot after their gods." — Exodus 34:15-16 (ASV)

Lest you make a covenant with the inhabitants. — If a covenant were made with the idolatrous nations of Canaan, and they were allowed to dwell in the land together with the Israelites (Exodus 23:33), the danger would be, in the first place, that Israel would be induced to partake in the idol-feasts; secondly, that intermarriages would take place; and thirdly, that such Israelites as married idolatrous wives would be persuaded by them to join in their worship, and would thus be seduced into actual idolatry. Solomon’s example shows the reality of the peril. (See 1 Kings 11:1–8.)