He confesses his sin and his unworthiness. Lord, I am not worthy to have you come under my roof. The Jewish elders said that he was worthy because of his works. That's how the Law looks at worthiness. But the soldier knew that all the charity in the world could not make him worthy to stand before Jesus.
Faith is humble.
It recognizes that God is holy, and I am not holy. I have nothing to offer God but brokenness and sin. I have no prior claim on God. I have no right to His favor. There is nothing in me that He should help me.