Thematic Bible: Passover first commemorated

Thus the LORD spoke to Moses in the wilderness of Sinai, in the first month of the second year after they had come out of the land of Egypt, saying, "Now, let the sons of Israel observe the Passover at its appointed time. "On the fourteenth day of this month, at twilight, you shall observe it at its appointed time; you shall observe it according to all its statutes and according to all its ordinances." read more.
So Moses told the sons of Israel to observe the Passover. They observed the Passover in the first month, on the fourteenth day of the month, at twilight, in the wilderness of Sinai; according to all that the LORD had commanded Moses, so the sons of Israel did.