For everyone who partakes only of milk is not accustomed to the word of righteousness, for he is an infant.
But solid food is for the mature, who because of practice have their senses trained to discern good and evil.
Hebrews 5:13-14 (NASB)
Practice righteousness
Little children, make sure no one deceives you; the one who practices righteousness is righteous, just as He is righteous;
the one who practices sin is of the devil; for the devil has sinned from the beginning. The Son of God appeared for this purpose, to destroy the works of the devil.
1 John 3:7-8 (NASB)