God Wants Your Kidney! The Use of “Kidneys” in the Bible

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For you formed my inward parts [kidneys];
you knitted me together in my mother’s womb.
I praise you, for I am fearfully and wonderfully made.

Psalm 139:13, 14a (ESV)

The human kidneys are two reddish-brown, bean-shaped organs located on the left and right in the abdominal cavity. In adult humans, the kidneys are about four and a half inches in length. Each is made up of about a million filtering units called nephrons, and healthy kidneys filter about a half cup of blood every minute, filtering all five quarts of blood in your body about thirty times each day. They remove impurities; they maintain a healthy balance of water, salts, and minerals, such as sodium, calcium, phosphorus, and potassium. They make hormones that help control blood pressure, and they make red blood cells and keep bones strong and healthy.

But in the Scriptures, the Hebrew term for kidney (kilyot) is not used to describe this cleansing function but rather to depict either the organ in the sacrificial animal or the inward part of a person—the way we today often use “heart.”

The Old Testament mentions the kidneys thirty-one times, and these references function in a number of ways. Eleven of those thirty-one instances refer to animal sacrifices (Exod 29 and Lev 3, 4, 7, 8, and 9 all refer to the context of sacrifices). Job refers to kidneys in regard to his experience of suffering: “God gives me up to the ungodly and casts me into the hands of the wicked…. He slashes open my kidneys and does not spare” (Job 16:11, 13b ESV).

The Hebrew word kilyot also takes another meaning, however, and in our English Bibles, it is most often translated as “heart/ inner being/mind.” Five passages picture God examining the kidneys to evaluate an individual: “I the Lord search the heart and test the mind [kidneys], to give every man according to his ways, according to the fruit of his deeds” (Jer 17:10 ESV; see also Jer 11:20 and Ps 26:2). In Jeremiah 12:1b–2 (ESV), the kidneys refer to hypocritical people whose words don’t match their true selves: “Why does the way of the wicked prosper?… you are near in their mouth and far from their heart [kidneys].” Proverbs 23:15–16 (ESV) identifies the kidneys as the origin of rejoicing: “My son, if your heart is wise, my heart too will be glad. My inmost being [my kidneys] will exult when your lips speak what is right.”

The New Testament uses the Greek word for kidneys, nephros, just once. It describes the searching work of Christ in his churches: “And all the churches will know that I am he who searches mind and heart [kidney]” (Rev 2:23b ESV).

What can we learn from the biblical references to kidneys? The kidneys are frequently associated with one’s deepest, innermost feelings. God seeks more than just surface emotions or mere words. He wants our innermost, deepest thoughts to evidence our true feelings for Him and in turn direct and motivate us to live for Him. God wants your kidney!

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