Numbers 9:10-11

10“Give the following instructions to the people of Israel: If any of the people now or in future generations are ceremonially unclean at Passover time because of touching a dead body, or if they are on a journey and cannot be present at the ceremony, they may still celebrate the Lord’s Passover.

11They must offer the Passover sacrifice one month later, at twilight on the fourteenth day of the second month. They must eat the Passover lamb at that time with bitter salad greens and bread made without yeast.