Declare his doings among the people; literally, among the peoples (comp. Psalms 9:11; Psalms 77:12; Psalms 107:22; Psalms 118:17). It is always regarded as one of man's chief duties to testify of God's goodness to others.
Here Israel is called upon to publish God's mercies and great deeds to the Gentiles. His name is exalted. God is in his Name, and his Name expresses his nature. As there is nothing so exalted in all the universe as God, so there is no name so exalted as his Name.
Hence his Name is protected by an express commandment.