John 7:17

If any man willeth to do his will, he shall know of the teaching, whether it is of God, or whether I speak from myself.

As in John 3:19-21, Jesus here again made the ability to believe on himself to turn on a question of will, and not of intelligence alone; and these remarks are the equivalent of his saying, "Look, if you really want to do the will of God, you will recognize that it is God's will, and not mine own, that I am proclaiming," There could also be further implications of this verse, as David Lipscomb noted:

Does not this involve the conclusion that if anyone in the world really desires to do the will of God, he will be brought to know that will? Is it possible that God would give his Son to die to open the way of salvation, and then leave one to die in ignorance of that way who would accept it if he knew it?[3]

The difficulty of finding out what is right in religion is a common complaint among men. They point to many differences among Christians and profess to be unable to decide what is right. (Such a person) should use what little knowledge he has got, and God will soon give him more.[4]

The source of knowing God's will is the Bible; but reason, intelligence, experience, obedience, and love are among the instruments by which true wisdom from its sacred pages may be won. And even more important than those instruments is that of the human will DESIRING to know the truth. Many accept blindly whatever teaching they received as a child without ever striving to know if it was really God's will that they learned. Ruskin warned against this:

Of all the insolent, and foolish persuasions that by any chance could enter and hold your empty little heart, this is the profoundest and foolishest, - that you have been so much the darling of heaven, and the favorite of the fates, as to be born in the nick of time, and in the punctual place, when and where pure divine truth had been sifted from the errors of the nations; and that your papa had been providentially disposed to buy a house in the convenient neighborhood of the steeple under which that immaculate and final verity would be proclaimed! Do not think it, child; it is not so.[5]

[3] David Lipscomb, A Commentary on the Gospel of John (Nashville: The Gospel Advocate Co., 1960), p. 111.

[4] J. C. Ryle, Expository Thoughts on the Gospels (Grand Rapids, Michigan: Zondervan Publishing House), p. 440.

[5] James Hastings, The Great Texts of the Bible (Edinburgh: T. and T. Clark), p. 307.