Albert Barnes Commentary Mark 9:15

"And straightway all the multitude, when they saw him, were greatly amazed, and running to him saluted him." — Mark 9:15 (ASV)

Were greatly amazed. They were astonished and surprised at his sudden appearance among them.

Saluted him. They received him with the customary marks of affection and respect. It is probable that this was not by any formal manner of salutation, but by the rush of the multitude, and by hailing him as the Messiah.