"... The position of the kidneys in the body makes them particularly inaccessible, and in cutting up an animal they are the last organs to be reached. Consequently, they were a natural symbol for the most hidden part of a man (Psalm 139:13), and in Job 16:13 to "cleave the kidneys asunder" is to effect the total destruction of the individual (compare Job 19:27; Lamentations 3:13). This hidden location, coupled with the sacred sacrificial use, caused the kidneys to be thought of as the seat of the innermost moral (and emotional) impulses. So the kidneys instruct (Psalm 16:7) or are "pricked" (Psalm 73:21), and God can be said to be far from the kidneys of sinners (Jeremiah 12:2). In all of these passages "conscience" gives the exact meaning. So the kidneys rejoice (Proverbs 23:16), cause torment (2 Esdras 5:34), or tremble in wrath (1 Maccabees 2:24). And to "know" or "try the kidneys" (usually joined with "the heart") is an essential power of God's, denoting His complete knowledge of the nature of every human being (Psalm 7:9; 26:2; Jeremiah 11:20; 17:10; 20:12; Wisdom of Solomon 1:6; Revelation 2:23) ..."