Psalms 132:16

I will also clothe her priests with salvation: and her saints shall shout aloud for joy.

God clothes His people with salvation when they comply with His word, and the condition is refusing to be conformed to the world, being transformed by the renewing of the mind, and discerning what is God's good and acceptable and perfect will. To be clothed with salvation is for God to endow His servants with wisdom and grace and strength and power for their testimony and preaching. This endowment is needed because they are weak when left to their own wisdom and strength, and must constantly look to Jesus as their strong Helper.

It is the holy unction that ministers must seek from God in secret prayer and sacred meditation rather than spending so much time in reading and study, imploring Him for heavenly wisdom and strength and power. Its purpose is that the truth they fully understand shall shine out before the people in its clearness and harmonious beauty and what they preach shall reach hearts. In this way preaching gains tremendous compelling power to draw every honest soul who loves the truth to embrace it, and because time is short and ministers in these last days are few, they must throw all their energies into the work and live in close connection with God and holy angels.