Proverbs 15:11 (ESV)

11 Sheol and Abaddon lie open before the LORD; how much more the hearts of the children of man!

“The heart is deceitful above all things and desperately sick; who can understand it? I the Lord search the heart and test the mind” (Jeremiah 17:9–10).

Happy are those people who fear the Lord from their hearts and can pray with David that the Lord will search them and know their hearts (Psalm 139:1–24). But for those who only pretend to fear God, this proverb must be terrifying to hear.