John Wesley on Numbers 9:1

In the first month - And therefore before the numbering of the people, which was not till the second month, Num 1:1,2. But it is placed after it, because of a special case relating to the passover, which happened after it, upon occasion whereof he mentions the command of God for keeping the passover in the wilderness, which was done but once, and without this command they had not been obliged to keep it at all, till they came to the land of Canaan.