Spiritual maturity means standing strong in obedience to the Lord Jesus and focusing on helping (serving) fellow Christians fulfill God’s purposes.
Peter explains the mature adds godliness and loving kindness to their lifestyle. He says, “and in [exercising] steadfastness [develop] godliness (piety), And in[exercising] godliness [develop] brotherly affection…” 2 Peter 1:6-7 AMP
In Ephesians 4:12-16 (NLT2) Paul adds, “Their responsibility is to equip God’s people to do his work and build up the church, the body of Christ. 13 This will continue until we all come to such unity in our faith and knowledge of God’s Son that we will be mature in the Lord, measuring up to the full and complete standard of Christ.
14 Then we will no longer be immature like children. We won’t be tossed and blown about by every wind of new teaching. We will not be influenced when people try to trick us with lies so clever they sound like the truth.”
“15 Instead, we will speak the truth in love, growing in every way more and more like Christ, who is the head of his body, the church.
16 He makes the whole body fit together perfectly. As each part does its own special work, it helps the other parts grow, so that the whole body is healthy and growing and full of love.”