Charles Ellicott Commentary 1 Chronicles 28:21

"And, behold, there are the courses of the priests and the Levites, for all the service of the house of God: and there shall be with thee in all manner of work every willing man that hath skill, for any manner of service: also the captains and all the people will be wholly at thy commandment." — 1 Chronicles 28:21 (ASV)

And, behold, the courses of the priests and the Levites. —The form of expression suggests that David pointed to them as he spoke. The representatives of religion would hardly be absent from an assembly of “all the princes of Israel” (1 Chronicles 28:1) (Compare to 1 Chronicles 24:5, “princes of God.”). They might also be included among “the valiant men.” (Compare to 1 Chronicles 9:13.)

And there shall be with thee for all manner of workmanship. —Rather, And with thee in every kind of work will be every volunteer with skill, for every kind of service: that is to say, skilled craftsmen have volunteered for the work (1 Chronicles 22:15), and will support your endeavors. The word rendered “volunteer” (nâdîb) strictly means one who offers free-will offerings. (Exodus 35:22; and the verb Judges 5:1, hithnaddçb.) The phrase “volunteer with wisdom,” or artistic skill, is not found elsewhere.

Also the princes and all the people. —Spoken, perhaps, with another gesture. The whole assembly would serve the wishes of Solomon.

Wholly at thy commandment. —Literally, For all thy words: i.e., orders (Vulgate, praecepta), or matters, business (1 Chronicles 26:32).