The LORD is your keeper: the LORD is your shade upon your right hand.
Read Chapter 121
Augustine of Hippo
AD 430
4. And who, thou askest, shall help me, save He who slumbereth not, nor sleepeth? Hear what followeth: "The Lord Himself is thy keeper" (ver. 5). It is not therefore man, that slumbereth and sleepeth, but the Lord, that keepeth thee. How doth He keep thee? "The Lord is thy defence upon the hand of thy right hand." ...It seemeth to me to have a hidden sense: otherwise he would have simply said, without qualification, "The Lord will keep thee," without adding, "on thy right hand." For how? Doth God keep our right hand, and not our left? Did He not create the whole of us? Did not He who made our right hand, make our left hand also? Finally, if it pleased Him to speak of the right hand alone, why said He, "on the hand of thy right hand," and not at once "upon thy right hand"? Why should He say this, unless He were keeping somewhat here hidden for us to arrive at by knocking? For He would either say, "The Lord shall keep thee," and add no more; or if He would add the right hand, "The Lord s...
6. Let us now come to this verse of the Psalm: "The Lord is thy defence upon the hand of thy right hand" (ver. 5). By hand he meaneth power. How do we prove this? Because the power of God also is styled the hand of God ...Whereof John saith, "He gave unto them power to become the sons of God." Whence hast thou received this power? "To them," he saith, "that believe in His Name." If then thou believest, this very power is given thee, to be among the sons of God. But to be among the sons of God, is to belong to the right hand. Thy faith therefore is the hand of thy right hand: that is, the power that is given thee, to be among the sons of God, is the hand of thy right hand ...
