Numbers 9 · a question people ask
Could anyone just keep the Passover in the second month instead?
No. The second date is for two kinds of people: whoever "is unclean by reason of a dead body, or is on a journey far away" (9:10). For everyone else the chapter is plain: "the man who is clean, and is not on a journey, and fails to keep the Passover, that soul shall be cut off from his people. Because he didn’t offer the offering of the LORD in its appointed season, that man shall bear his sin" (9:13). The men in 9:7 had asked why they could not "offer the offering of the LORD in its appointed season"; 9:13 uses the same words for the man who could and didn't.
The verses
“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 the LORD in its appointed season among the children of Israel?””