4. This was a sarcastic remark that was made by the opponents, for they did not acknowledge that the admonition had been sent down to the Prophet (peace be upon him): otherwise they could not say that he was insane. What they really meant by this remark was: You, who claim that the admonition has been sent down to you, are insane. A similar remark was also made by Pharaoh concerning Prophet Moses (peace be upon him). Addressing his courtiers, he said: The Messenger who has been sent to you is insane. (Surah Ash-Shuara, Ayat 27).
5. “We do not send down the angels.” We do not send down the angels for the mere fun of it in response to the request of the people, nor are they sent to unveil the reality before them in order to show to them all the unseen things to which the Messengers invite them to believe. As a matter of fact, angels are sent down on that occasion when it is decreed to pass judgment on sane wicked people. At that time the judgment comes into operation without extending any invitation to the condemned people to accept the message, for their period of respite ends as soon as the reality is unveiled before them. “Except with truth.”
They bring down truth with them. That is, they come down to eradicate falsehood and to establish truth in its stead. Or, in other words, it means, they come down to put into force the judgment of Allah.