Let the children of Israel also keep the passover,.... Though this ordinance was enjoined the people of Israel, and observed by them at the time of their coming out of Egypt, and had been since repeated, Leviticus 23:5; yet without a fresh precept, or an explanation of the former, they seemed not to be obliged, or might not be sensible that they were obliged to keep it, until they came into the land of Canaan, Exodus 12:25; and therefore a new order is given them to observe it:
at his appointed season; and what that season is is next declared.

THE PASSOVER ENJOINED. (Numbers 9:1-5)
Let the children of Israel also keep the passover at his appointed season, &c.--The date of this command to keep the passover in the wilderness was given shortly after the erection and consecration of the tabernacle and preceded the numbering of the people by a month. (Compare Numbers 9:1 with Numbers 1:1-2). But it is narrated after that transaction in order to introduce the notice of a particular case, for which a law was provided to meet the occasion. This was the first observance of the passover since the exodus; and without a positive injunction, the Israelites were under no obligation to keep it till their settlement in the land of Canaan (Exodus 12:25). The anniversary was kept on the exact day of the year on which they, twelve months before, had departed from Egypt; and it was marked by all the peculiar rites--the he lamb and the unleavened bread. The materials would be easily procured--the lambs from their numerous flocks and the meal for the unleavened bread, by the aid of Jethro, from the land of Midian, which was adjoining their camp (Exodus 3:1). But their girded loins, their sandaled feet, and their staff in their hand, being mere circumstances attending a hurried departure and not essential to the rite, were not repeated. It is supposed to have been the only observance of the feast during their forty years' wandering; and Jewish writers say that, as none could eat the passover except they were circumcised (Exodus 12:43-44, Exodus 12:48), and circumcision was not practised in the wilderness [Joshua 5:4-7], there could be no renewal of the paschal solemnity.