We can gauge how important the quality of humility is to our relationship with God by considering the setting of this statement. It appears in the Sermon on the Mount, three whole chapters in which Jesus lays out before His followers the foundational teaching that, if followed, will work to produce a good relationship with God. The foundation of the foundation, we might say, is the Beatitudes, and the very first quality He presents, implying its prime necessity, is poverty of spirit.
Poverty of spirit is the diametric opposite of the haughty, competitive, self-assertive, self-sufficient arrogance of pride that says, "This is the way I see it." Being poor in spirit has absolutely nothing to do with being hard up in one's circumstances—in fact, it has nothing to do with the physical realm. It is a fundamental part of the spiritual realm, of which God and the purity of His attitudes, character, and truths are the central elements.
"Poor in spirit" is poverty as compared to God's qualities. It is poverty in terms of Holy Spirit. It is to be destitute in regard to the fruit and power of God's Holy Spirit of which we all desperately need. This attitude is the product of self-evaluation in which a person, comparing his own spiritual qualities to God's, finds himself utterly impoverished of any virtue of value to eternal life. Not only that, he finds himself utterly unable, powerless, to help himself to become like God.
Thus, a person who is poor of spirit clearly sees and appreciates his dependence on God both physically and spiritually. Humility is a fruit of the realization of his complete dependence. He is nothing in his own eyes and knows that his proper place is face down in the dust before God.
The apostle John writes in I John 5:4-5, "For whatever is born of God overcomes the world. And this is the victory that has overcome the world—our faith. Who is he who overcomes the world, but he who believes that Jesus is the Son of God." The honest recognition of need, the desire to glorify God, and the practice of overcoming leads a called-out one to live by faith.
Jesus Christ is the One that God has assigned to oversee and empower us. He is the Helper and Advocate (I John 2:1) who goes alongside, enabling us to be created in His image. From Him, we draw spiritual strength, and He gives grace to the humble.