So, where does David get the right to insert new instruments into temple worship? On our way to the Bible’s answer, let’s consider the temple itself. Where is the authority for a temple? After all, the law of Moses goes into detail about making a portable tent (a tabernacle), not a solid building (a temple). It predicts a permanent location for formal worship, which later turns out to be Jerusalem. But the law gives no plan for a stone temple. Do David and Solomon act on their own initiative regarding the temple? Or do they follow God’s lead?
We would expect the latter to be true. Remember, David becomes king after Saul. Why does God dethrone Saul? Because Saul keeps acting on his own initiative (1 Samuel 13:1-14; 15:1-23). Now David, preparing his son for kingship, continually stresses doing everything in the way God has revealed. For example, in 1 Chronicles 28, David emphasizes God’s conditional promise about Solomon’s reign. God says of Solomon,
I will establish his kingdom forever if he is unswerving in carrying out My commands and laws, as is being done at this time. (1 Chronicles 28:7)
“As is being done” refers to David’s practice of careful obedience to God. In that same chapter, 1 Chronicles 28, David goes on to answer our question about authority for the temple. (Note the inspiration and authority indicated by the parts we italicize.)
He [David] gave him [Solomon] the plans of all that the Spirit had put in his mind for the courts of the temple of the LORD and all the surrounding rooms, for the treasuries of the temple of God and for the treasuries for the dedicated things. He gave him instructions for the divisions of the priests and Levites, and for all the work of serving in the temple of the LORD, as well as for all the articles to be used in its service…. “All this,” David said, “I have in writing from the hand of the LORD upon me, and He gave me understanding in all the details of the plan.” (1 Chronicles 28:12-13, 19)
No, David does not act on a whim of his own. We find instead that God’s Spirit plainly reveals to David every aspect—“all the details”—of the temple and its services. These specifics are not a case of human autonomy, but of divine authority.