There are two types of maturity: natural maturity and divine maturity.
Natural maturity is considered as full development. In agriculture, fruit is only considered mature when it is ripe. If it is premature, it could be dangerous to eat. How do you know you are mature? Man and God define maturity differently. Ephesians 4:12-15 says “to equip his people for works of service, so that the body of Christ may be built up until we all reach unity in the faith and in the knowledge of the Son of God and become mature, attaining to the whole measure of the fullness of Christ. Then we will no longer be infants, tossed back and forth by the waves, and blown here and there by every wind of teaching and by the cunning and craftiness of people in their deceitful scheming. Instead, speaking the truth in love, we will grow to become in every respect the mature body of him who is the head, that is, Christ.” Service is the key to maturity.