Easton's Bible Dictionary (1897)/Reins

Reins
 * Reins 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.).