Jamieson, Fausset and Brown on Mark 9:15

15. And straightway all the people--the multitude.

when they beheld him, were greatly amazed--were astounded.

and running to him saluted him--The singularly strong expression of surprise, the sudden arrest of the discussion, and the rush of the multitude towards Him, can be accounted for by nothing less than something amazing in His appearance. There can hardly be any doubt that His countenance still retained traces of His transfiguration-glory. (See Ex 34:29, 30). So Bengel, De Wette, Meyer, Trench, Alford. No wonder, if this was the case, that they not only ran to Him, but saluted Him. Our Lord, however, takes no notice of what had attracted them, and probably it gradually faded away as He drew near; but addressing Himself to the scribes, He demands the subject of their discussion, ready to meet them where they had pressed hard upon His half-instructed and as yet timid apostles.