“But speaking the truth in love, may grow up into him in all things, which is the head, even Christ:”
Ephesians 4:15

God expects that we grow up into Christ in all things.
When you got born again, you became a new man in Christ, a true child of the living God:
“That which is born of the flesh is flesh; and that which is born of the Spirit is spirit. Marvel not that I said unto thee, Ye must be born again.” John 3:6-7
“Beloved, now are we the sons of God…” (1 John 3:2)
And as is expected of every child, God expects you to grow spiritually, he is the father of spirits (Hebrews 12:9) after all:
“As newborn babes, desire the sincere milk of the word, that ye may grow thereby:” 1 Peter 2:2
When he says grow spiritually, he doesn’t mean become more diabolical, instead the main verse makes it clear who you are to grow up into- Christ!
He expects you to grow in your knowledge of the son of God for one purpose- that you become truly like him in everything:
“…unto a perfect man, unto the measure of the stature of the fulness of Christ:” Ephesians 4:13

Bible Reading Plan: Isahiah 52, Leviticus 17