1 Chronicles 29:9, commentary and pictures

The people rejoiced because they had offered willingly to the Lord, with perfect heart and sincere, wholehearted purpose, and David the king also rejoiced with great joy in their willing giving. Their willing gifts were a source of gladness both to the givers and to the king, since joy came through freely giving with wholehearted devotion. The offerings that brought this joy were given for the temple, the house of God, and the work of building it. It was freewill giving for the Lord's temple that made the people and David glad together.

David had made extensive preparations for the house of God and had given generously from his own treasury, and the willingness of the people followed his example. David himself was not to carry out the building work, for Solomon, not David, was to do the building.

The willingness to give came from God, who had supplied their possessions and by His Spirit moved their hearts to offer them, so the glory belonged to Him. Their willing generosity reflected a disposition God had placed in them, since what they gave had come from Him for His work. Willing gifts are an expression of a perfect heart toward God. The offerings expressed a desire to return to God what is His and to devote abilities and service to His work, modeling willing, wholehearted service rather than half-hearted duty.