I have set the Lord always before me - By night as well as by day; in my private meditations as well as in my public professions. I have regarded myself always as in the presence of God; I have endeavored always to feel that, his eye was upon me. This, too, is one of the certain characteristics of piety, that we always feel that we are in the presence of God, and that we always act as if his eye were upon us. Compare the notes at Acts 2:25.
Because he is at my right hand - The right hand was regarded as the post of honor and dignity, but it is also mentioned as a position of defense or protection. To have one at our right hand is to have one near us who can defend us. Thus, in Psalms 109:31, “He shall stand at the right hand of the poor, to save him,” etc. So Psalms 110:5, “The Lord at thy right hand shall strike through kings in the day of his wrath.” Psalms 121:5, “the Lord is thy Keeper; the Lord is thy shade upon thy right hand.” The idea is, that as we use the right hand in our “own” defense, we seem to have an additional and a needed helper when one is at our right hand. The sense here is, that the psalmist felt that God, as his Protector, was always near him; always ready to interpose for his defense. We have a somewhat similar expression when we say of anyone that he is “at hand;” that is, he is near us.
I shall not be moved - I shall be safe; I shall not be disturbed by fear; I shall be protected from my enemies. See Psalms 10:6; Psalms 15:5. Compare Psalms 46:5. The language here is that of one who has confidence in God in time of great calamities, and who feels that he is safe under the divine favor and protection.