The implication of Verse 118 was that those who persisted in their denial of the Holy Prophet ﷺ did so out of sheer malice and ignorance, and could not be expected to reform themselves. Since he has been sent as the mercy for all the worlds", the thought of their being incorrigible was likely to make him sad on their account. So, in this verse Allah offers him a consolation. He has been sent down to men, bearing the truth and the genuine faith. His function is twofold -- to give glad tidings to those who accept the truth, and warnings of dire punishment to those who deny. Allah assures him that he will not be held responsible or taken to account for those who willingly pursue the way to Hell. All that he is required to do is to keep performing his own function, and not to worry as to who accepts the truth and who does not.