The following is an excerpt from
The MacArthur New Testament Commentary on Luke 7.
For this reason I did not even consider myself worthy to come to You, but just say the word, and my servant will be healed. “For I also am a man placed under authority, with soldiers under me; and I say to this one, ‘Go!’ and he goes, and to another, ‘Come!’ and he comes, and to my slave, ‘Do this!’ and he does it.” Now when Jesus heard this, He marveled at him, and turned and said to the crowd that was following Him, “I say to you, not even in Israel have I found such great faith.” (Luke 6:7-9)
Instead of having Jesus enter his house, the centurion proposed that He just say the word, and his servant would be healed. He was absolutely confident that the Lord spoke with divine power and authority, as the illustration he gave reveals For I also am a man placed under authority, with the soldiers under me; and I say to this one, ‘Go!’ and he goes, and to another, ‘Come!’ and he comes, and to my slave, ‘Do this!’ and he does it.” As a military commander, the centurion was under the authority of his superior officers and used to obeying their orders. He also knew what it meant to give orders to the soldiers serving under him, as well as his slave, and have them obeyed. He understood that Jesus had that same authority over life and death.
When Jesus heard this remarkable expression of the centurion’s humble faith, He marveled at him. Here is a glimpse of Jesus’ true humanity, since as God He is omniscient and cannot be surprised by anything. But just as in His humanity He became tired (John 4:6), hungry, (Matt. 4:2), and thirsty (John 19:28; cf. 4:7), so also could He be astonished at the faith displayed by this Roman soldier.