Charles H. Spurgeon on Psalms 132:9

Let thy priests be clothed with righteousness. No garment is so resplendent as that of a holy character. In this glorious robe our great High priest is evermore strayed, and he would have all his people adorned in the same manner. Then only are priests fit to appear before the Lord, and to minister for the profit of the people, when their lives are dignified with goodness. They must ever remember that they are God's priests, and should therefore wear the livery of their Lord, which is holiness: they are not only to have righteousness, but to bc clothed with it, so that upon every part of them righteousness shall be conspicuous. Whoever looks upon God's servants should see holiness if they see nothing else. Now, this righteousness of the ministers of the temple is prayed for in connection with the presence of the Lord; and this instructs us that holiness is only to be found among those who commune with God, and only comes to them through his visitation of their spirits. God will dwell among a holy people; and on the other hand, where God is the people become holy. And let thy saints shout for joy. Holiness and happiness go together; where the one is found, the other ought never to be far away. Holy persons have a right to great and demonstrative joy: they may shout because of it. Since they are saints, and thy saints, and thou hast come to dwell with them, O Lord, thou hast made it their duty to rejoice, and to let others know of their joy. The sentence, while it may read as a permit, is also a precept: saints are commanded to rejoice in the Lord. Happy religion which makes it a duty to be glad! Where righteousness is the clothing, joy may well be the occupation.