A.T. Robertson Commentary Matthew 8:10

"And when Jesus heard it, he marvelled, and said to them that followed, Verily I say unto you, I have not found so great faith, no, not in Israel." — Matthew 8:10 (ASV)

So great faith (τοσαυτην πιστιν). In a Roman centurion and greater than in any of the Jews. In like manner Jesus marvelled at the great faith of the Canaanitish woman (Matthew 15:28).