Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) said about this verse: "And We did not make the vision which We showed you except as a trial for the people" [Surah al-Isra': 60]. He said: "It is the vision which the Prophet (peace and blessings be upon him) saw on the night of the Ascension (Mi'raj); it is not a vision of sleep."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 11591