Here's the advice. Sanctify means "set Him apart." It means in this case, "make God the focus of your thinking; make God the focus of your approach to life; make God the focus of the circumstance that you find yourself in."
Is that not what Peter forgot in Matthew 16? The disinformation was the focus of Peter's response to Jesus—not God's thoughts. If God's thoughts, if God's word, had really been sanctified in Peter's heart at that time, he never would have said what he did. He would have said something like, "Yes, Jesus, I understand. That's what the scripture says." But instead, he disagreed with God. When one sanctifies God in his heart, then the word of God becomes the focus, not the word from the spirit of this world.
