Growing in Salvation
You're human your whole life. In fact, you're human in the womb. What it means to be human is that you are meant to grow from birth through life. With salvation you're saved your entire life and into eternity, but just like a newborn baby you have to grow because that is part of being human and being saved. Part of salvation is growing.
Therefore, putting aside all malice and all guile and hypocrisy and envy and all slander, like newborn babes, long for the pure milk of the word, that by it you may grow in respect to salvation. (1 Peter 2:1-2)
It would be tragic for a baby never to grow or to have a disorder that would permanently stunt his growth. A newborn baby is a delight; a childlike adult is a tragedy. Peter continued the comparison of us with children saying, like a baby we too should be fanatical about being fed. What feeds us is the wonderful word of God. Believing it we experience the new birth, and studying it and integrating it into our lives we experience spiritual growth. We are born again to grow!