When I was a child, I spoke as a child, I understood as a child, I thought as a child; but when I became a man, I put away childish things. – 1 Cor 13:11
The essence of the letter to the churches in Ephesus is that we as followers of Christ, need to grow up. Maturity is being like Christ, not living like the world, but instead walking worthy of our calling. It is a challenging word, but a good one. Jesus has called us to live a life of maturity in him.