Numbers 9:6, 10

Now there were certain men who were defiled by a human corpse, so that they could not keep the Passover on that day; and they came before Moses and Aaron that day.

“Speak to the children of Israel, saying: ‘If anyone of you or your posterity is unclean because of a corpse, or is far away on a journey, he may still keep the LORD’s Passover.