Verse 13. For thou hast possessed my reins. Thou art the owner of my inmost parts and passions: not the indweller and observer only, but the acknowledged lord and possessor of my most secret self. The word "reins" signifies the kidneys, which by the Hebrews were supposed to be the seat of the desires and longings; but perhaps it indicates here the most hidden and vital portion of the man; this God doth not only inspect, and visit, but it is his own; he is as much at home there as a landlord on his own estate, or a proprietor in his own house.
Thou hast covered me in my mother's womb. There I lay hidden -- covered by thee. Before I could know thee, or aught else, thou hadst a care for me, and didst hide me away as a treasure till thou shouldest see fit to bring me to the light. Thus the Psalmist describes the intimacy which God had with him. In his most secret part -- his reins, and in his most secret condition -- yet unborn, he was under the control and guardianship of God.
EXPLANATORY NOTES AND QUAINT SAYINGS
Verse 13. Thou hast possessed my reins. From the sensitiveness to pain of this part of the body, it was regarded by the Hebrews as the seat of sensation and feeling, as also of desire and longing ( Psalms 72:21 Job 16:13 19:27). It is sometimes used of the inner nature generally ( Psalms 16:7 Jeremiah 20:12 ), and specially of the judgment or direction of reason (Jer 11:20 12:2). --William Lindsay Alexander, in Kitto's Cyclopaedia.
Verse 13. Thou hast possessed my reins. The reins are made specially prominent in order to mark them, the seat of the most tender, most secret emotions, as the work of him who trieth the heart and the reins. --Franz Delitzsch.
Verse 13. Thou hast covered me in my mother's womb. The word here rendered cover means properly to interweave; to weave; to knit together, and the literal translation would be, "Thou hast woven me in my mother's womb", meaning that God had put his parts together, as one who weaves cloth, or who makes a basket. So it is rendered by De Wette and by Gesenius (Lex.). The original word has, however, also the idea of protecting, as in a booth or hut, woven or knit together, -- to wit, of boughs and branches. The former signification best suits the connection; and then the sense would be, that as God had made him -- as he had formed his members, and united them in a bodily frame and form before he was born -- he must be able to understand all his thoughts and feelings. As he was not concealed from God before he saw the light, so he could not be anywhere. --Albert Barnes.