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 ( Psalms 7:9 ; 16:7 ; 26:2 ; 139:13 ; Jeremiah 17:10 , etc.).

These dictionary topics are from
M.G. Easton M.A., D.D., Illustrated Bible Dictionary, Third Edition,
published by Thomas Nelson, 1897. Public Domain, copy freely.