John Gill

And when he had thus spoken,.... What was so right and reasonable, in so becoming a manner, without heat or passion: one of the officers which stood by; it may be one of those who had been sent to him and had been a hearer of him, whom Jesus might look wistfully at, or point unto, when he said the above words, at which he might be provoked: and therefore stroke Jesus with the palm of his hand; or gave him a rap with a rod, or smote him with a staff, as some think, is the sense of the phrase; though the Syriac, agreeably to our version, reads it, he smote him, , "upon his cheek"; gave him, what we commonly call, a slap on the face; and which is always esteemed a very great affront, and was a piece of rudeness and insolence to the last degree in this man: saying, answerest thou the high priest so? This he said, as well as gave the blow, either out of flattery to the high priest, or to clear himself from being a favourer of Christ; which, by what had been said, he might think would be suspected: some have thought this was Malchus, whose ear Christ had healed; if so, he was guilty of great ingratitude.