Exodus 34:17

Don't make a covenant with the inhabitants of the land, lest they play the prostitute after their gods, and sacrifice to their gods, and one call you and you eat of his sacrifice;

and you take of their daughters to your sons, and their daughters play the prostitute after their gods, and make your sons play the prostitute after their gods.

You shall keep the feast of unleavened bread. Seven days you shall eat unleavened bread, as I commanded you, at the time appointed in the month Abib; for in the month Abib you came out from Egypt.

All that opens the womb is mine; and all your livestock that is male, the firstborn of cow and sheep.