At that time the Lord separated the tribe of Levi,.... Not at the time that Moses came down from the mount with the tables of the law, but some considerable time after, even after the tabernacle was erected; nor at the time that Aaron died, and Eleazar succeeded him, but many years before that; unless there was a fresh separation of them, or a renewal of it when Eleazar became high priest in his father's stead; and so that being mentioned is the reason of its being repeated here: to bear the ark of the covenant of the Lord; even that into which the law, sometimes called the covenant, was put, and therefore here called the ark of the covenant: when this was carried from place to place, as it was especially in the wilderness, it was the business of the Levites to bear it, particularly the Kohathites; Num 3:31, to stand before the Lord to minister unto him; that is, to his priests, in the tabernacle, and to keep and guard that: and to bless in his name unto this day; not to bless the people, which was the work of the priest, but to sing praise in the name of the Lord, to give thanks unto him, and bless and praise him.