Numbers 9:6-11

And there were certain men who were unclean through touching a dead body, so that they could not keep the Passover on that day, and they came before Moses and Aaron on that day. And those men said to him, “We are unclean through touching a dead body. Why are we kept from bringing the LORD’s offering at its appointed time among the people of Israel?” And Moses said to them, “Wait, that I may hear what the LORD will command concerning you.” The LORD spoke to Moses, saying, “Speak to the people of Israel, saying, If any one of you or of your descendants is unclean through touching a dead body, or is on a long journey, he shall still keep the Passover to the LORD. In the second month on the fourteenth day at twilight they shall keep it. They shall eat it with unleavened bread and bitter herbs.