By nature, Simon Peter was brash, vacillating, and undependable. He tended to make promises he couldn’t follow through with and appeared to lunge wholeheartedly into something only to bail out before finishing. When Jesus first met Simon, He gave him the nickname Peter, which means “Rock.” It appears He wanted the new name to be perpetual reminder to him about who he should be. Whenever He called him Rock, the Lord was commending His student for acting the way he ought to be acting.
When the Lord calls a disciple, He not only knows who he or she is, He also knows who he or she should be – and will be. If He can make a vacillating character like Peter as stable as a rock, He can also transform our character flaws and make us stand at the very point where we would otherwise fail. Thus His strength is perfected in our weakness (2 Corinthians 12:9). Have you seen that pattern in your own spiritual growth?
-MacArthur in “From the Ordinary to the Extraordinary” devotional