Numbers 9:7-11

Those men said to him, “Though we are unclean because of a dead person, why are we kept from presenting the offering of the Lord at its appointed time among the sons of Israel?”

Moses then said to them, “Wait, and I will listen to what the Lord will command concerning you.”

Then the Lord spoke to Moses, saying,

“Speak to the sons of Israel, saying, ‘If any one of you or of your generations becomes unclean because of a dead person, or is on a distant journey, he may, however, celebrate the Passover to the Lord.

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