Allah says to His Messenger , encouraging him to convey the Message and informing him that He is protecting him from the people, that He is able to deal with them and that they are in His grasp and under His domination and control.
وَإِذْ قُلْنَا لَكَ إِنَّ رَبَّكَ أَحَاطَ بِالنَّاسِ
(And (remember) when We told you: "Verily, your Lord has encompassed mankind..") Mujahid, `Urwah bin Az-Az-Zubayr, Al-Hasan, Qatadah and others said, "This means, He protected you from them."
وَمَا جَعَلْنَا الرُّءْيَا الَّتِى أَرَيْنَـكَ إِلاَّ فِتْنَةً لِّلنَّاسِ
(And We made not the vision which We showed you but a trial for mankind,) Al-Bukhari recorded that Ibn `Abbas said:
وَمَا جَعَلْنَا الرُّءْيَا الَّتِى أَرَيْنَـكَ إِلاَّ فِتْنَةً لِّلنَّاسِ
(And We made not the vision which We showed you but a trial for mankind,) "This is the vision which the Messenger of Allah ﷺ saw with his own eyes on the night when he was taken on the Night Journey (Al-Isra').
وَالشَّجَرَةَ الْمَلْعُونَةَ فِى القُرْءَانِ
and (likewise) the accursed tree in the Qur a0n. refers to the Tree of Zaqqum." This was also recorded by Ahmad, `Abdur-Razzaq and others. It was also reported by Al-`Awfi from Ibn `Abbas. It was also interpreted as referring to the Night of the Isra' by Mujahid, Sa`id bin Jubayr, Al-Hasan, Masruq, Ibrahim, Qatadah, `Abdur-Rahman bin Zayd and several others. We have already quoted at length a comprehensive collection of Hadith about the Isra' at the beginning of this Surah, praise be to Allah. We have also already stated that some people gave up their Islam after they had been following the truth, because their hearts and minds could not comprehend that, and they denied what their knowledge could not grasp, but Allah caused it to increase and strengthen the faith of others, and so He says:
إِلاَّ فِتْنَةً
(but a trial), meaning a test. As for the cursed tree, this is the Tree of Zaqqum. When the Messenger of Allah ﷺ told them that he had seen Paradise and Hell, and seen the Tree of Zaqqum, they did not believe that, and Abu Jahl, upon whom be the curses of Allah, even said, "Bring us some dates and butter," and he started eating them and saying, "Let us have some Zaqqum, we don't know any other Zaqqum but this." This was narrated by Ibn `Abbas, Masruq, Abu Malik, Al-Hasan Al-Basri and others. Everyone who interpreted the Ayah to refer to the Night of the Isra', also interpreted it to refer to the Tree of Zaqqum.
وَنُخَوِّفُهُمْ
(We make them afraid) meaning, `We make the disbelievers afraid with Our warnings and punishments and torment.'
فَمَا يَزِيدُهُمْ إِلاَّ طُغْيَانًا كَبِيرًا
(but it only increases them in naught save great disbelief, oppression and disobedience to Allah.) means, it only pushes them further into their disbelief and misguidance, and this is because Allah has forsaken them.