ESV scriptures dealing with false converts.
John 17:3 “And this is eternal life, that they know you the only true God, and Jesus Christ whom you have sent.”
Titus 1:16 “They profess to know God, but they deny him by their works. They are detestable, disobedient, unfit for any good work.”
Heb 12:14 “Strive for peace with everyone, and for the holiness without which no one will see the Lord.”
2 Cor 13:5 “Examine yourselves, to see whether you are in the faith. Test yourselves. Or do you not realize this about yourselves, that
Jesus Christ is in you?—unless indeed you fail to meet the test!”
1 John 3:10 “By this it is evident who are the children of God, and who are the children of the devil: whoever does not practice righteousness is not of God, nor is the one who does not love his brother.”