Verse 22. For song - He was the moderator of the musick, instructing them when and how to lift up their voices, or change their notes, or make their stops.
23. Door-keepers - They were appointed to keep the door of the tent in which the ark was to be kept, that no unallowed person might press in and touch it; and in like manner they were to attend upon the ark in the way, and to guard it from the press and touch of prophane hands; for which end these two went before the ark, is their other two brethren mentioned in the close of ver. 24, came after it.
Verse 26. Helped - Encouraging them in their work with some comfortable sign of his presence with them. In all our religious exercises, we must derive help from heaven. God's ministers that bare the vessels of the Lord, have special need of divine help in their ministrations, that God may be glorified thereby, and the people edified.
Verse 27. Linen - With a linen ephod. This circumstance is repeated, because it was an unusual thing for one, who was no Levite, to wear a Levitical garment.