Jesus said these things in the synagogue, as he taught at Capernaum.
59. He spoke these things in the synagogue. John points out the place, that we may know that there were many present, and likewise, that a sermon was delivered as on a weighty and important subject. But it immediately follows that out of so great a multitude there were scarcely to be found a very few who profited by it; and — what is worse...
Whether this conference was with the Capernaites, in whose synagogue Christ now was, or with those who came from the other side of the sea, is not certain nor material; however, it is an instance of Christ's condescension that he gave them leave to ask him questions, and did not resent the interruption as an affront, no, not from his common hearers, though not his immediate followers.
Commenting on John 6:28-59
When Jesus knew in himself,.... And of himself, without any intelligence from others, or hearing what was said, being the omniscient God: that his disciples murmured at it; at the doctrine he had delivered, looking upon it as absurd, incredible, and contrary to sense and reason: he said unto them, does this offend you? or trouble you? cannot you get over this? cannot you understand it? or account for it?