Psalms 138:4

All the kings of the earth shall praise thee, O LORD, when they hear the words of thy mouth.

All the kings of the earth will praise the Lord when they hear the words of His mouth. That praise is worship directed toward His holy temple because of His lovingkindness and truth. The Lord's word reveals His glory, and hearing it leads those who hear it to praise Him.

The verse is encouragement to those who have washed their robes white in the blood of the Lamb and who meet severe trials. It calls them to stand firm under resistance, to honor Christ who redeemed them, and to keep genuine conversion and a renewed heart. They are to stay sweet under trial and to reveal divine grace, overcoming by the blood of the Lamb and the word of testimony until welcomed at last into the city of God. Taken hold of with soul-longing, faith, and prayer, it fills lips with thanksgiving and praise and brings encouragement and hope to weary and discouraged souls. It lifts the downcast and worried from discouragement to rejoice in the Lord, showing a living hope expressed in living service.