Numbers 9:5-7

New International Version - UK

⁵ and they did so in the Desert of Sinai at twilight on the fourteenth day of the first month. The Israelites did everything just as the Lord commanded Moses.

⁶ But some of them could not celebrate the Passover on that day because they were ceremonially unclean on account of a dead body. So they came to Moses and Aaron that same day ⁷ and said to Moses, ‘We have become unclean because of a dead body, but why should we be kept from presenting the Lord’s offering with the other Israelites at the appointed time?’