Thou therefore, my son, be strong in the grace that is in Christ Jesus. (2 Timothy 2:1)
Timothy was not the son of Paul in a physical way. He was his spiritual son in the sense that it was under Paul's ministry that this young man had turned to Christ. A child of God is born into God's family by means of his faith in Christ. "Being born again, not of corruptible seed, but of incorruptible, by the word of God, which liveth and abideth for ever" (1 Peter 1:23). Timothy is in the family of God, and he is a child of God.
I love this — "be strong in grace." My friend, if you think that you can grit your teeth and go out and live the Christian life on your own, you're in for a great disappointment. If you feel that you can follow a few little rules or some clever gimmicks to make you a mature Christian, then you have fallen into a subtle trap of legalism. Paul gives no rules, and the Word of God has no rules to tell the child of God how to live the Christian life. We are saved by grace, and now we are to live by the grace of God and be strong in that grace.
Let me give you an example from my boyhood. My dad traveled a great deal in his work, and he always put down a few rules for me to follow while he was away. Some of them I obeyed. I had to cut the wood, and I didn't mind that. But my father had some other rules that I frankly didn't go for. I hate to admit this, but one of those rules was that I should attend Sunday school. The interesting thing is that he never went himself, but he always made me go. Anyway, when he was away from home, I didn't go. One time I was fishing, and he came home suddenly and found me. I had just pulled out a fish, turned around, and there stood my dad. He said, "Son, are you having any luck?" Well, my luck ran out right at that moment! I appealed to him and admitted that I had done wrong, and by grace he was good to me. I really took advantage of his good nature and the fact that I was his son.
My father died when I was fourteen, but now I have a heavenly Father, and I sure do appeal to His grace. When things go wrong down here, I go to Him and appeal to Him. When I fail, I don't run from Him like I used to. I have found that when I am away from Him, the whipping He gives me hurts lots worse. I don't want to get out at the end of that switch where it really stings. I come in close to Him, and the closer I am the less it hurts. I am a son of my heavenly Father. What a marvelous figure of speech!
When I hear Christians say, "I don't do this, and I don't do that, and I am following a set of rules," I immediately recognize that they know very little about the grace of God. They are trying to live the Christian life in their own strength. But Paul says, "Be strong in the grace that is in Christ Jesus."
—From Edited Messages on 2 Timothy by Dr. J. Vernon McGee