Numbers 9:4-6  Amplified Bible, Classic Edition

⁴ So Moses told the Israelites they should keep the Passover.

⁵ And they kept the Passover on the fourteenth day of the first month in the evening in the Wilderness of Sinai; according to all that the Lord commanded Moses, so the Israelites did.

⁶ And there were certain men who were defiled by touching the dead body of a man, so they could not keep the Passover on that day; and they came before Moses and Aaron on that day.