‘And all bore him witness, and wondered at the words of grace which proceeded out of his mouth. And they said, “Is not this Joseph's son?”
They all took note of what He had said. This probably refers not only to His opening words, but also to words which followed. Luke is only giving us the gist of what is being said. From what follows we would expect to read antagonism in this verse, and it can in fact be read like that. They bore witness to what He said, were quite astonished at it, even though they were words of grace, and queried how Joseph's son could talk like this. Other, however see it as their at first being impressed by Him, but eventually reacting when they remembered Who He was.
‘Bore witness' could mean favourably or antagonistically. The fact that they wondered at how he could speak such gracious words might suggest that it meant favourably, in which case the atmosphere is to be seen as changing when they suddenly shook themselves and realised Who it was Who was speaking. He was only the local carpenter! But it may be that they were antagonistic from the start, even though they had to admit that for a carpenter He spoke well.
Or it may be that here Luke is describing the words from the onlookers point of view. They are words proclaiming the grace of God. But these people were so hardened that these words of grace did not touch them, and instead raised their antagonism.
And then they looked at one another in even more wonder, and said, “Is this not Joseph's son?” They could not understand it. Here was the village carpenter and yet He was speaking such profound and impossible words. The words that follow demonstrate that they were not happy about it. They felt that He was taking too much on Himself. And they no doubt recognised that there had been none of the miracles in Nazareth that they had heard had happened in Capernaum.