1 Chronicles 25:1

And captains All the princes of Israel, with the priests and the Levites, whom David gathered together (1Ch 23:2) for this very end, that, with their approbation and consent, all these things might be established, who are here fitly called the captains of the host; for the princes were, under David, the chief captains of the militia of the kingdom; and as the Levites are called a host, and the Lord's host, because of their number and order in holy ministrations, so these priests and Levites were the captains and governors of the rest. Separated Distributed them into their several ranks: which, though chiefly done by David as a prophet, and by divine direction, yet is imputed in part to the captains of the host, because it was done with their concurrence and approbation. The service To the service of God, under the conduct of these persons. Who should prophesy Praise God by singing the psalms of David, and other sacred songs made by themselves, who were prophets, or by other prophets or holy men of God. The number of the workmen according to their service Although this sacred work of praising God is here termed service, and the persons employed in it workmen, yet it is the greatest liberty and pleasure to be engaged in it. But the expressions intimate that it is our duty to make a business of it, and stir up all that is within us to it; and that in our present state of corruption and infirmity, it will not be done, as it should be done, without labour and struggle. We must take pains with our hearts to bring and keep them to this work, and to engage all that is within us in it. It is probable, Heman, Asaph, and Jeduthun were bred up under Samuel, and had their education in the schools of the prophets, of which he was the founder and president. Then they were pupils, now they come to be masters. Those that would be eminent must begin early and take time to prepare themselves. This good work, of singing God's praises, Samuel revived and set on foot, but lived not to see it brought to the perfection in which it appears here. Solomon perfects what David began. So David perfects what Samuel began. Let each in their day do what they can for God and his church, though they cannot carry it so far as they would; when they are gone, God can out of stones raise up others, who shall build upon their foundation, and bring forth the top-stone.