The first question is, “It this really true to the Bible?” They would argue from 1 Corinthians 12:8 that it is. (I have my doubts, but at least they have a verse using this expression.) The follow-up question, is, “Even if there is such a thing as a ‘word of knowledge’ is this what you will receive, and will it be consistent with Scriptures?” In New Testament days at least there was the “gift of tongues.” But even admitting there is such a gift, there are abuses of that gift (as Paul deals with in 1 Corinthians), and there may well be counterfeits of it as well. I guess what I’m saying is that I would not try to convince someone that there is no such thing as this “word of knowledge,” but rather that this must conform to the rest of the teachings of the Word of God. In other words, is the guidance that he will be given “wise” in the biblical sense of that word.
You might want to look at this lesson from Proverbs which I did a number of years ago.
Dr. Bruce Waltke has an excellent little book on Knowing the Will of God, which deals more extensively with this matter.
I get very concerned about present day “revelations,” which, in practical terms, seem to carry more weight than the Word of God. Further, I think that godly counsel is a good source of input as to God’s will, as opposed to consulting a kind of “spiritual guru,” who tells you God’s will for your life.
If I sound a little “soft” here, perhaps I am a bit, but I am still working on a very strong refutation of the current “prophecy” movement, led by some respected evangelical scholars (such as Wayne Grudem), who say that prophecy today is not the prophecy of the Old Testament, or the New, but is “like” it. This “new” prophecy is not an infallible word from God, but a fallible impression of God’s will. This kind of thing scares me. In the Old Testament, if a person claimed to be a prophet and was wrong, he was to be stoned. Today, some tell us that we are to expect fallible prophets and prophecies. That’s both amazing and frightening.
On clear word from God is 1 Thessalonians 5:19-21. We are not to despise prophetic utterances, Paul says, but neither are we to blindly accept them as true. We are to examine them carefully, and cling only to what is good. This assumes that not all prophecies are good. This passage may carry more weight than anything, because it is a clear and direct word from God on the very thing he is seeking.