*Minor differences ignored. Grouped by changes, with first version listed as example.
The Gershonites and Merarites are superintended by Ithamar, Aaron's younger son, who had already had the oversight of the tabernacle in its construction Exodus 38:21. Thus, readily do the permanent offices of the leaders of the Israelite community spring out of the duties which, under the emergencies of the first year of the Exodus, they had been led, from time to time, to undertake.
This [is] the service of the families of the sons of Gershon in the tabernacle of the congregation: and their charge [shall be] under the (q) hand of Ithamar the son of Aaron the priest.
(q) Under the charge and oversight.
This is the service of the families of the sons of Gershon,.... Which they should execute when the camp and tabernacle were in motion:
in the tabernacle of the congregation in the court; where they should take up their burdens, or which lie in things respecting the tabernacle; this was the part they were to be employed in, namely, in taking care of the hangings of the tabernacle, &c.
and their charge shall be under the hand of Ithamar the son of Aaron the priest; the things committed to their care were delivered by him to them, and they were under his inspection and direction.
their charge shall be under the hand of Ithamar the son of Aaron, &c.--The Levites were generally subject to the official command of the priests in doing the ordinary work of the tabernacle. But during the journeyings Eleazar, who was next in succession to his father, took the special charge of the Kohathites [Numbers 4:16], while his brother Ithamar had the superintendence of the Gershonites and Merarites [Numbers 4:33].
"Their charge (mishmereth) is in the hand of Ithamar," i.e., is to be carried out under his superintendence (cf. Exodus 38:21).
Under the hand - Under his conduct and direction.
*More commentary available at chapter level.