Narrated Ibn `Abbas:
(regarding the Verse) "And We granted the vision (Ascension to the heavens "Miraj") which We showed you (O Muhammad as an actual eye witness) but as a trial for mankind.' (17.60): Allah's Apostle actually saw with his own eyes the vision (all the things which were shown to him) on the night of his Night Journey to Jerusalem (and then to the heavens). The cursed tree which is mentioned in the Qur'an is the tree of Az-Zaqqum.
Narrated Ibn `Abbas:
Regarding the Statement of Allah" "And We granted the vision (Ascension to the heavens) which We made you see (as an actual eye witness) was only made as a trial for the people." (17.60) Ibn `Abbas added: The sights which Allah's Messenger (ﷺ) was shown on the Night Journey when he was taken to Bait-ulMaqdis (i.e. Jerusalem) were actual sights, (not dreams). And the Cursed Tree (mentioned) in the Qur'an is the tree of Zaqqum (itself) .
Narrated Ibn `Abbas:
Regarding: 'And We granted the vision (Ascension to the Heaven "Miraj") which We showed you (O Muhammad as an actual eye witness) but as a trial for mankind.' (17.60) It was an actual eyewitness which was shown to Allah's Messenger (ﷺ) during the night he was taken on a journey (through the heavens). And the cursed tree is the tree of Az-Zaqqum (a bitter pungent tree which grows at the bottom of Hell).