The kidneys, the supposed seat of the desires and affections; used metaphorically for “heart.” The “reins” and the “heart” are often mentioned together, as denoting the whole moral constitution of man (Ps. 7:9; 16:7; 26:2; 139:13; Jer. 17:10, etc.).

(i.e. kidneys). In the ancient system of physiology the kidneys were believed to be the seat of desire and longing, which accounts for their often being coupled with the heart. (Psalms 7:9; 26:2; Jeremiah 11:20; 17:10), etc.