David said to all the assembly, Now bless Yahweh your God. All the assembly blessed Yahweh, the God of their fathers, and bowed down their heads, and worshiped Yahweh, and the king.
So David is, has told of his own commitment and now he's challenging them for a commitment of giving to God. "This is what I have done. This is what I propose to do. Now who of you are willing to offer your service unto the Lord?"