John Gill Commentary Numbers 9:13

"But the man that is clean, and is not on a journey, and forbeareth to keep the passover, that soul shall be cut off from his people; because he offered not the oblation of Jehovah in its appointed season, that man shall bear his sin." — Numbers 9:13 (ASV)

But the man that [is] clean
Free from any pollution by a dead body, or the like:

and is not in a journey ;
in a distant country; for if he was on a journey in his own nation, he ought to return and attend the passover, which all the males from the several parts of the land were obliged unto; wherefore the Vulgate Latin version of (Numbers 9:10) ; is a wrong one; "or in a way afar off in your nation"; for at whatsoever distance they were in their own nation, they were bound to appear:

and forbeareth to keep the passover ;
the first passover in the first month, the month Nisan, wilfully, through negligence, or not caring to be at the expense and trouble of it, or on any pretence whatsoever: Ben Gersom interprets it of one that will not keep neither the first nor the second passover:

even the same soul shall be cut off from his people ;
either be excommunicated from them, or cut off by death by the immediate hand of God:

because he brought not the offering of the Lord in his appointed
season :
this is the ground and reason of the resentment; it was a breach of the divine command, which required this offering; ingratitude to God, being a thank offering for a singular deliverance; and this aggravated by its not being brought at the appointed time, which was the fit ti me for it:

that man shall bear his sin ;
be chargeable with the guilt of it, and bear the punishment of it; he on himself, as Aben Ezra notes, he, and he only; not his wife and family, for he being the head and master of the family, it lay upon him to provide the passover lamb for himself and his house.