Observe that His emphasis is on their application, not on whether we know about them or even understand them.
In this verse, Christ makes a very positive statement: We will be happy if we put this teaching into practice. He knew that grudges, hate, anger, and lack of forgiveness do nothing but shackle us and hinder our spiritual growth. If we let them hang around, they will eventually destroy us. Forgiving even those who have done things spitefully against us (Matthew 5:44) unlocks our shackles and releases us from feelings of animosity. When we rid ourselves of these burdens, we can find inner peace and true happiness.
Bill Keesee (1935-2010)
Another Look at Footwashing
Jesus teaches self-denial to His disciples not only with His words but also by His actions. Notice that His call to self-denial comes immediately after predicting His own sacrificial death. He is the supreme model of the self-denial to which He calls others. He even denies Himself any urge to avenge Himself or to threaten His persecutors for what they had done to Him. In Jesus' example, we see that, by committing ourselves to God who judges rightly, we deny ourselves the temptation of worldly lusts.
Martin G. Collins
Overcoming (Part 5): Self-Denial
The word translated happy in the King James and New King James Bibles can easily be rendered "blessed," "favored," or "satisfied." There is a reward for following God's marvelous way of life! Not only will we be given eternal life and rulership in His Kingdom, but God will also bestow His blessing and favor upon us until we are completely satisfied!
Richard T. Ritenbaugh
Holy Days: Atonement
Other Forerunner Commentary entries containing John 13:17:
1 Peter 5:5