William Burkitt on John 13:17

Our Lord here intimates unto us these two things:

1. The necessity of knowledge, in order unto practice.

2. The necessity of practice, in order unto happiness.

A man may know the will of God indeed, and not do it; but he can never do the will of God (acceptably) and not know it. The knowledge of God's will and our duty, is necessary to the practice of it. The knowledge of our duty, and the practice of it, may be and too often are separated; but the practice of religion, and doing what we know to be our duty is the only way to true happiness.

Learn thence, 1. That Christ doth not approve of a blind obedience in his people, but requires that their practice and obedience be founded upon understanding and knowledge.

2. That the first care of those that will be Christ's disciples and followers must be this, with all seriousness to apply themselves to the knowlege of their Master's will.

3. That next to the knowlege of our duty, our first and chief care must be, to practice everything that we understand and know to be our duty.

4. That a right knowledge and practice of our duty, will certainly make us happy: If ye know these things, happy are ye if ye do them.