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 eye-witness which was shown to Allah's Apostle 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).
• Sahih al-Bukhari, Vol. 6, Book of Prophetic Commentary on the Qur'an, Hadith 240
• Sahih al-Bukhari, Book of Prophetic Commentary on the Qur'an, Hadith 240