[The account of the nobleman in John 4:46-54] presents us with a beautiful example of the characteristics and nature of faith, namely, that it is to increase and become perfect. It portrays faith as something which does not lie quiet and idle, but is something living, restless, which either regresses or progresses, which lives and moves. If this does not happen, then it is not faith, but a dead idea in the heart about God, for true, living faith, which the Holy Spirit pours into the heart, simply cannot be idle. I say this so that no one will be secure, thinking that once he has laid hold of faith he will persist in it. What is important is not the beginning, but continuing, more and more as time goes on, and increasing and learning to know God better.
– Luther (LW 79:233)