The altar, to wit, of burnt-offerings, and incense too, as appears from the matter of their offerings. The singular number for the plural. Not for the first dedication of them, for it is apparent they were dedicated or consecrated before this time by Moses and Aaron for divers days together, Le 8 Le 9; but for a further dedication of them, these being the first offerings that were made for any particular persons or tribes. In the day, i.e. about the time, as soon as it was anointed. See Poole Numbers 7:1.
Related Commentaries of Numbers 7:10
Numbers 7:10
10 And the princes offered for dedicating of the altar in the day that it was anointed, even the princes offered their offering before the altar.