A Commentary, Critical, Practical, and Explanatory on the Old and New Testaments, by Robert Jamieson, A.R. Fausset and David Brown  at sacred-texts.com
num 9:2THE PASSOVER ENJOINED. (Num 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 Num 9:1 with Num 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 (Exo 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 (Exo 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 (Exo 12:43-44, Exo 12:48), and circumcision was not practised in the wilderness [Jos 5:4-7], there could be no renewal of the paschal solemnity.
num 9:6A SECOND PASSOVER ALLOWED. (Num 9:6-14)
there were certain men, who were defiled by the dead body of a man--To discharge the last offices to the remains of deceased relatives was imperative; and yet attendance on a funeral entailed ceremonial defilement, which led to exclusion from all society and from the camp for seven days. Some persons who were in this situation at the arrival of the first paschal anniversary, being painfully perplexed about the course of duty because they were temporarily disqualified at the proper season, and having no opportunity of supplying their want were liable to a total privation of all their privileges, laid their case before Moses. Jewish writers assert that these men were the persons who had carried out the dead bodies of Nadab and Abihu [Lev 10:4-5].
num 9:8Moses said unto them, Stand still, and I will hear what the Lord will command concerning you--A solution of the difficulty was soon obtained, it being enacted, by divine authority, that to those who might be disqualified by the occurrence of a death in their family circle or unable by distance to keep the passover on the anniversary day, a special license was granted of observing it by themselves on the same day and hour of the following month, under a due attendance to all the solemn formalities. (See on Ch2 30:2). But the observance was imperative on all who did not labor under these impediments.
num 9:14if a stranger shall sojourn among you, and will keep the passover--Gentile converts, or proselytes, as they were afterwards called, were admitted, if circumcised, to the same privileges as native Israelites, and were liable to excommunication if they neglected the passover. But circumcision was an indispensable condition; and whoever did not submit to that rite, was prohibited, under the sternest penalties, from eating the passover.
num 9:15A CLOUD GUIDES THE ISRAELITES. (Num 9:15-23)
the cloud covered the tabernacle--The inspired historian here enters on an entirely new subject, which might properly have formed a separate chapter, beginning at this verse and ending at Num 10:29 [CALMET]. The cloud was a visible token of God's special presence and guardian care of the Israelites (Exo 14:20; Psa 105:39). It was easily distinguishable from all other clouds by its peculiar form and its fixed position; for from the day of the completion of the tabernacle it rested by day as a dark, by night as a fiery, column on that part of the sanctuary which contained the ark of the testimony (Lev 16:2).
num 9:17when the cloud was taken up--that is, rose to a higher elevation, so as to be conspicuous at the remotest extremities of the camp. That was a signal for removal; and, accordingly, it is properly called (Num 9:18) "the commandment of the Lord." It was a visible token of the presence of God; and from it, as a glorious throne, He gave the order. So that its motion regulated the commencement and termination of all the journeys of the Israelites. (See on Exo 14:19).
num 9:19when the cloud tarried long upon the tabernacle, . . . then Israel kept the charge of the Lord, and journeyed not--A desert life has its attractions, and constant movements create a passionate love of change. Many incidents show that the Israelites had strongly imbibed this nomad habit and were desirous of hastening to Canaan. But still the phases of the cloud indicated the command of God: and whatsoever irksomeness they might have felt in remaining long stationary in camp, "when the cloud tarried upon the tabernacle many days, they kept the charge of the Lord, and journeyed not." Happy for them had they always exhibited this spirit of obedience! and happy for all if, through the wilderness of this world, we implicitly follow the leadings of God's Providence and the directions of God's Word!