Albert Barnes Commentary Mark 5:20

"And he went his way, and began to publish in Decapolis how great things Jesus had done for him: and all men marvelled." — Mark 5:20 (ASV)

In Decapolis. See Barnes' notes on Matthew 4:25.

How great things, etc. This was the natural expression of right feeling at being cured of such a calamity. So the desire of sinners freed from sin is to honour Jesus; to ascribe all to his power; and to invite the world to participate in the same salvation, and to join them in doing honour to the Son of God. Compare Psalm 66:16.