The Lord is thy keeper - Thy Preserver; thy Defender. He will keep time from danger; he will keep thee from sin; he will keep thee unto salvation.
The Lord is thy shade - The Lord is as a shadow: as the shadow of a rock, a house, or a tree, in the intense rays of the burning sun. See the notes at Isaiah 25:4.
Upon thy right hand - See Psalm 16:8; Psalm 109:31. Perhaps the particular allusion to the right hand here may be that that was the place of a protector. He would thus be at hand, or would be ready to interpose in defense of him whom he was to guard. It is possible, however, that the idea here may be derived from the fact that in Scripture the geographer is represented as looking to the east, and not toward the north, as with us. Hence, the south is always spoken of as the right, or at the right hand (compare the notes at Psalm 89:12); and as the intense rays of the sun are from the south, the idea may be, that God would be as a shade in the direction from which those burning rays came.

The Lord is thy keeper,.... This explains more fully who it is that keeps Israel and particular believers, and confirms the same; not a creature, but the Lord; the Word of the Lord, as the Targum, in Psalm 121:7, Christ, the Word and Wisdom of God; who is the keeper of his people by the designation of his Father, who has put them into his hands to be kept by him; and by their full will and consent, who commit the keeping of their souls to him; for which he is abundantly qualified, being able as the mighty God; faithful to him that has appointed him; tender and compassionate to those under his care, whom he keeps as the apple of his eye; and diligent and constant, for he keeps them night and day, lest any hurt them: he keeps them as they are his flock, made his care and charge; as they are the vineyard of the Lord of hosts; as they are a city, which, unless the Lord keeps, the watchmen watch in vain; as they are his body and members of it, and as they are his jewels and peculiar treasure: these he keeps in the love of God; in his own hands; in the covenant of grace; in an estate of grace; and in his own ways, safe to his kingdom and glory;
the Lord is thy shade upon thy right hand; he is at the right hand of his people, to hold their right hand; to teach them to go, lead them into communion with himself, and hold them up safe; and to strengthen their right hand, assist them in working, without whom they can do nothing; and to counsel and direct them, and to protect and defend them against all their enemies. So a shadow signifies defence; see Numbers 14:9, Ecclesiastes 7:12; and such great personages are to others; in which sense Virgil (n) uses the word "shadow"; and much more true is this of God himself. And he is like the shadow of a great rock in a weary land; or of a spreading tree, which is a protection from heat, and very reviving and refreshing; see Isaiah 32:2. The allusion may be to the pillar of cloud by day, which guided and guarded the Israelites in the wilderness, and was a shadow from the heat, Isaiah 4:5; as Christ is from the heat of a fiery law, the flaming sword of justice, the wrath of God, and the fiery darts of Satan.
(n) "Et magnum reginae nomen obumbrat", Aeneid. l. xi.

upon thy right hand--a protector's place (Psalm 109:31; Psalm 110:5).

That which holds good of "the Keeper of Israel" the poet applies believingly to himself, the individual among God's people, in Psalm 121:5 after Genesis 28:15. Jahve is his Keeper, He is his shade upon his right hand (היּמין as in Judges 20:16; 2-Samuel 20:9, and frequently; the construct state instead of an apposition, cf. e.g., Arab. jânbu 'l-grbı̂yi, the side of the western = the western side), which protecting him and keeping him fresh and cool, covers him from the sun's burning heat. על, as in Psalm 109:6; Psalm 110:5, with the idea of an overshadowing that screens and spreads itself out over anything (cf. Numbers 14:9). To the figure of the shadow is appended the consolation in Psalm 121:6. הכּה of the sun signifies to smite injuriously (Isaiah 49:10), plants, so that they wither (Psalm 102:5), and the head (Jonah 4:8), so that symptoms of sun-stroke (2-Kings 4:19, Judith 8:2f.) appears. The transferring of the word of the moon is not zeugmatic. Even the moon's rays may become insupportable, may affect the eyes injuriously, and (more particularly in the equatorial regions) produce fatal inflammation of the brain.
(Note: Many expositors, nevertheless, understand the destructive influence of the moon meant here of the nightly cold, which is mentioned elsewhere in the same antithesis. Genesis 31:40; Jeremiah 36:30. De Sacy observes also: On dit quelquefois d'un grand froid, comme d'un grand chaud, qu'il est brulant. The Arabs also say of snow and of cold as of fire: jaḥrik, it burns.)
From the hurtful influences of nature that are round about him the promise extends in Psalm 121:7-8 in every direction. Jahve, says the poet to himself, will keep (guard) thee against all evil, of whatever kind it may be and whencesoever it may threaten; He will keep thy soul, and therefore thy life both inwardly and outwardly; He will keep (ישׁמר־, cf. on the other hand ישׁפּט־ in Psalm 9:9) thy going out and coming in, i.e., all thy business and intercourse of life (Deuteronomy 28:6, and frequently); for, as Chrysostom observes, ἐν τούτοις ὁ βίος ἅπας, ἐν εἰσόδοις καὶ ἐξόδοις, therefore: everywhere and at all times; and that from this time forth even for ever. In connection with this the thought is natural, that the life of him who stands under the so universal and unbounded protection of eternal love can suffer no injury.

Shade - To keep thee from the burning heat of the sun.