Numbers 9:9

Those men said to him, "We are unclean because of the dead body of a man. Why are we kept back, that we may not offer the offering of Yahweh in its appointed season among the children of Israel?

Moses answered them, "Wait, that I may hear what Yahweh will command concerning you.

Say to the children of Israel, 'If any man of you or of your generations is unclean by reason of a dead body, or is on a journey far away, he shall still keep the Passover to Yahweh.

In the second month, on the fourteenth day at evening they shall keep it; they shall eat it with unleavened bread and bitter herbs.