Jeremiah 17:9-10 KJV The heart is deceitful above all things, and desperately wicked: who can know it? [10] I the Lord search the heart, I try the reins, even to give every man according to his ways, and according to the fruit of his doings. People pretend well, when the rubber meets the road, that's how you know. Romans 16:17-18 KJV Now I beseech you, brethren, mark them which cause divisions and offences contrary to the doctrine which ye have learned; and avoid them. [18] For they that are such serve not our Lord Jesus Christ, but their own belly; and by good words and fair speeches deceive the hearts of the simple.