Numbers 9:1-5

ISV(i) 1 The Passover at Sinai
The LORD spoke to Moses in the Wilderness of Sinai during the first month of the second year that they had left Egypt, 2 “The Israelis are to observe the Passover at its appointed time 3 on the fourteenth day of this month. You are to observe it at this appointed time between the evenings. You are to observe it according to all its decrees and laws.”
4 So Moses instructed the Israelis to observe the Passover. 5 They observed the Passover on the fourteenth day of the first month at twilight, in the Wilderness of Sinai. The Israelis did everything that the LORD had commanded through Moses.