by J. C. Ryle
Peter asked, "Lord, why can't I follow you now? I will lay down my life for You!"
Then Jesus answered, "Will you really lay down your life for Me? I tell you the truth, before the rooster crows, you will deny Me three times!" John 13:37-38
These verses show us how much self-ignorance there may be in the heart of a true believer. We see Peter declaring that he was ready to lay down his life for his Master. We see his Master telling Peter that he would deny Him three times. And we all know how the matter ended. The Master was right — and Peter was wrong.
Let it be a settled principle in our religion, that there is an amount of weakness in all our hearts of which we have no adequate conception, and that we never know how far we might fall if we were tempted. We imagine sometimes, like Peter, that there are some wicked things which we could not possibly do. We look pitifully upon others who fall, and please ourselves in the thought that we would not have done so.
We know nothing at all. The seeds of every sin are latent in our hearts, even when renewed, and they only need occasion, or carelessness and the withdrawal of God's grace for a season — to put forth an abundant crop. Like Peter, we may think we can do wonders for Christ — and like Peter, we may learn by bitter experience that we have no power and strength at all.
The servant of Christ will do wisely to remember these things. "Let him that thinks he stands, take heed lest he fall." (1 Corinthians 10:12.) A humble sense of our own innate weakness, a constant dependence on the Strong for strength, a daily prayer to be preserved, because we cannot preserve ourselves — these are the true secrets of safety!
Let us watch jealously over our hearts, and beware of giving way to the beginnings of sin. Happy is he who fears always, and walks humbly with his God. The strongest Christian is the one who feels his weakness most, and cries most frequently, "Hold me up — and I shall be safe!" (Psalm 119:117.)
Excerpt from Ryle's exposition on the Gospel of John in Expository Thoughts on the Gospels