1 John 2:21

Overview - 1 John 2
He comforts them against the sins of infirmity.
Rightly to know God is to keep his commandments;
to love our brethren;
15 and not to love the world.
18 We must beware of seducers;
20 from whose deceits the godly are safe, preserved by perseverance in faith, and holiness of life.
Treasury of Scripture Knowledge

1 John 2:21  (King James Version)
I have not written unto you because ye know not the truth, but because ye know it, and that no lie is of the truth.

because ye know not
Proverbs 1:5 ; Proverbs 9:8 Proverbs 9:9 Romans 15:14 Romans 15:15 ; 2 Peter 1:12