Thematic Bible: Special passover, for those who were unclean, or on a journey, to be held in the second month

But there were some men who were unclean because of the dead person, so that they could not observe Passover on that day; so they came before Moses and Aaron on that day. Those men said to him, "Though we are unclean because of the dead person, why are we restrained from presenting the offering of the LORD at its appointed time among the sons of Israel?" Moses therefore said to them, "Wait, and I will listen to what the LORD will command concerning you." read more.
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, observe the Passover to the LORD. 'In the second month on the fourteenth day at twilight, they shall observe it; they shall eat it with unleavened bread and bitter herbs. 'They shall leave none of it until morning, nor break a bone of it; according to all the statute of the Passover they shall observe it.

For the king and his princes and all the assembly in Jerusalem had decided to celebrate the Passover in the second month, since they could not celebrate it at that time, because the priests had not consecrated themselves in sufficient numbers, nor had the people been gathered to Jerusalem. Thus the thing was right in the sight of the king and all the assembly.