I am still reading Dallas Willard's Hearing God but I have begun to love and appreciate Proverbs 20:27, and what Willard wrote about the still small voice, being one of the ways how God speaks to us. He said,
The final means through which God addresses us is our own spirits—our own thoughts and feelings toward ourselves as well as toward events and people around us. This, I believe, is the primary subjective way that God addresses us. Of all the ways in which a message comes from within the experience of the person addressed (such as dreams and visions or other mental states), the form of one’s own thoughts and attendant feelings is the most common path for hearing God for those who are living in harmony with God. Of all the possible subjective routes, this mode is best suited to the redemptive purposes of God because, once again, it most engages the faculties of free, intelligent beings involved in the work of God as his colaborers and friends.
Thus the familiar King James Version of Proverbs 20:27 says, “The spirit of man is the candle of the Lord, searching all the inward parts of the belly.” This is possibly better put in the Jerusalem Bible: “Man’s spirit is the lamp of Yahweh, searching his deepest self.”
In a passage of great importance to our exploration here, the apostle Paul makes a comparison between humans and God regarding self-knowledge: “For what human being knows what is truly human except the human spirit that is within? So also no one comprehends what is truly God’s except the Spirit of God” (1 Cor 2:11). Paul then points out that we have received the Spirit of God and concludes that we can therefore search out and know the very mind of God by means of his Spirit—in contrast to the proverb quoted earlier, which emphasizes the Lord’s use of our spirit. After quoting the question from Isaiah 40:13, “Who has directed the spirit of the Lord, or as his counselor has instructed him?” the apostle replies, “But we have the mind of Christ” (1 Cor 2:16).
So God uses our self-knowledge or self-awareness, which is heightened and given a special quality by his presence and direction, to search us out and reveal to us the truth about ourselves and our world. And we are able to use his knowledge of himself—made available to us in Christ and the Scriptures—to understand in some measure his thoughts and intentions toward us and to help us see his workings in our world.
Source: Dallas Willard, Hearing God: Developing a Conversational Relationship with God, IVP, 2012.