Deuteronomy 13:4

13:4 You must follow the Lord your God and revere only him; and you must observe his commandments, obey him, serve him, and remain loyal to him.

Deuteronomy 16:1

The Passover-Unleavened Bread Festival

16:1 Observe the month Abib and keep the Passover to the Lord your God, for in that month he brought you out of Egypt by night.