Exodus 12:1
And the Lord spake unto Moses and Aaron in the land of Egypt, saying,
Cross-reference
Exodus 40:2
Historical context
Exodus 40:2 shows the tabernacle set up on the first day of the first month, using the calendar established here.
Numbers 9:2
Parallel
Numbers 9:2 commands the Israelites to celebrate Passover at its appointed time, directly referencing this original institution.
Ezekiel 45:21
Parallel
Ezekiel 45:21 commands Passover in the first month on the 14th day, echoing the law given here.