Christ compliments the centurion's faith because it is faith in His Word. When the centurion says he is unworthy of Christ's presence, he tells Him that he believed that all that He had to do was speak and the miracle would happen. To explain his understanding of the principle, the centurion says, "For I also am a man under authority, having soldiers under me; and I say to this man, 'Go,' and he goes" (Matthew 8:9). He recognizes the power of the spoken word because he is familiar with authority, yet he also believes that Christ's word has power and authority even over disease. In asking Jesus to heal simply by speaking, the centurion shows that he accepted the authority of Christ's word. No one can have real faith if they reject the Word of God.
It is impossible to please God without faith (Hebrews 11:6). Many people doubt whether God's Word is sufficient. If they have a problem, they run instead to hear what the world's doctors and psychiatrists have to say. Today, many professing Christian churches do not show very much confidence in God's Word either. The centurion's "only speak a word" is not an applicable command for most churches. These days, churches use a lot of entertainment to draw people into their membership, believing that it is essential to their success. Yet, "only speak a word" is the true essence of spiritual success. Without the Word of God, the church will not maintain a solid foundation of truth and grow.
Martin G. Collins
The Miracles of Jesus Christ: Healing a Centurion's Servant (Part Three)