There is something astonishing to me – and, I now see, thrilling – whenever the Scriptures say that Jesus “marveled” over something. That God the Son should be filled with wonder, or astonishment, or surprise is in itself a marvel.

He marveled at the Centurion’s faith. This Roman soldier’s faith, a Gentile, was greater than any He had seen in Israel. Why? Because, unlike the Jewish elders, whose argument for Jesus to come help him was his worthiness, he knew himself to be unworthy. And he understood the power of word/command and Jesus’ authority to accomplish His will by them.

So the slave is healed. Luke gives us no other response from Jesus other than His expression of wonder. There is no healing command mentioned. The messengers go home, and find the slave in good health.

I think I am more like the Jews than the Roman soldier.

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.”

(NASB)
Luke 7:9