Reins - Vine's Expository Dictionary of New Testament Words

Reins

[ 1,,G3510, nephros ]
a kidney" (Eng., "nephritis," etc.), usually in the plural, is used metaphorically of "the will and the affections," Revelation 2:23, "reins" (cp. Psalms 7:9; Jeremiah 11:20; Jeremiah 17:10; Jeremiah 20:12). The feelings and emotions were regarded as having their seat in the "kidneys."

Vine's Expository Dictionary of New Testament Words