2 Chronicles 29:25

And he appointed, according to the order of David his father, the courses of the priests to their service, and the Levites to their charges, to praise and minister before the priests, as the duty of every day required: the porters also by their courses at every gate: for so had David the man of God commanded.

Moreover four thousand were porters; and four thousand praised the LORD with the instruments which I made, said David, to praise therewith.

And these are the singers, chief of the fathers of the Levites, who remaining in the chambers were free: for they were employed in that work day and night.

For when David was up in the morning, the word of the LORD came unto the prophet Gad, David’s seer, saying,

And the singers the sons of Asaph were in their place, according to the commandment of David, and Asaph, and Heman, and Jeduthun the king’s seer; and the porters waited at every gate; they might not depart from their service; for their brethren the Levites prepared for them.

And with them Heman and Jeduthun with trumpets and cymbals for those that should make a sound, and with musical instruments of God. And the sons of Jeduthun were porters.

Also in Judah the hand of God was to give them one heart to do the commandment of the king and of the princes, by the word of the LORD.

All this, said David, the LORD made me understand in writing by his hand upon me, even all the works of this pattern.

Now the acts of David the king, first and last, behold, they are written in the book of Samuel the seer, and in the book of Nathan the prophet, and in the book of Gad the seer,

And the LORD spake unto Gad, David’s seer, saying,

And the pattern of all that he had by the spirit, of the courts of the house of the LORD, and of all the chambers round about, of the treasuries of the house of God, and of the treasuries of the dedicated things: