Numbers 9:1, 5, 11

In the first month of the second year after their departure from the land of Egypt, the LORD told Moses in the Wilderness of Sinai

and they observed it in the first month on the fourteenth day at twilight in the Wilderness of Sinai. The Israelites did everything as the LORD had commanded Moses.

Such people are to observe it in the second month, on the fourteenth day at twilight. They are to eat the animal with unleavened bread and bitter herbs