Charles H. Spurgeon on Psalms 121:5

The Lord is thy keeper. Here the preserving One, who had been spoken of by pronouns in the two previous verses, is distinctly named —Jehovah is thy keeper. What a mint of meaning lies here: the sentence is a mass of bullion, and when coined and stamped with the king's name it will bear all our expenses between our birthplace on earth and our rest in heaven. Here is a glorious person —Jehovah, assuming a gracious office and fulfilling it in person, —Jehovah is thy keeper, in behalf of a favoured individual —thy, and a firm assurance of revelation that it is even so at this hour —Jehovah is thy keeper. Can we appropriate the divine declaration? If so, we may journey onward to Jerusalem and know no fear; yea, we may journey through the valley of the shadow of death and fear no evil. The Lord is thy shade upon thy right hand. A shade gives protection from burning heat and glaring light. We cannot bear too much blessing; even divine goodness, which is a right hand dispensation, must be toned down and shaded to suit our infirmity, and this the Lord will do for us. He will bear a shield before us, and guard the right arm with which we fight the foe. That member which has the most of labour shall have the most of protection. When a blazing sun pours down its burning beams upon our heads the Lord Jehovah himself will interpose to shade us, and that in the most honourable manner, acting as our right hand attendant, and placing us in comfort and safety. "The Lord at thy right hand shall smite through kings". How different this from the portion of the ungodly ones who have Satan standing at their right hand, and of those of whom Moses said, "their defence has departed from them". God is as near us as our shadow, and we are as safe as angels.