Sahih Muslim Book - 1, Hadith - 409

و حَدَّثَنَا زُهَيْرُ بْنُ حَرْبٍ حَدَّثَنَا الْوَلِيدُ بْنُ مُسْلِمٍ حَدَّثَنَا الْأَوْزَاعِيُّ قَالَ سَمِعْتُ يَحْيَى يَقُولُ سَأَلْتُ أَبَا سَلَمَةَ أَيُّ الْقُرْآنِ أُنْزِلَ قَبْلُ؟ قَالَ { يَا أَيُّهَا الْمُدَّثِّرُ } فَقُلْتُ أَوْ اقْرَأْ فَقَالَ سَأَلْتُ جَابِرَ بْنَ عَبْدِ اللَّهِ أَيُّ الْقُرْآنِ أُنْزِلَ قَبْلُ قَالَ { يَا أَيُّهَا الْمُدَّثِّرُ } فَقُلْتُ أَوْ اقْرَأْ قَالَ جَابِرٌ أُحَدِّثُكُمْ مَا حَدَّثَنَا رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ جَاوَرْتُ بِحِرَاءٍ شَهْرًا فَلَمَّا قَضَيْتُ جِوَارِي نَزَلْتُ فَاسْتَبْطَنْتُ بَطْنَ الْوَادِي فَنُودِيتُ فَنَظَرْتُ أَمَامِي وَخَلْفِي وَعَنْ يَمِينِي وَعَنْ شِمَالِي فَلَمْ أَرَ أَحَدًا ثُمَّ نُودِيتُ، فَنَظَرْتُ فَلَمْ أَرَ أَحَدًا ثُمَّ نُودِيتُ فَرَفَعْتُ رَأْسِي فَإِذَا هُوَ عَلَى الْعَرْشِ فِي الْهَوَاءِ يَعْنِي جِبْرِيلَ عَلَيْهِ السَّلَام فَأَخَذَتْنِي رَجْفَةٌ شَدِيدَةٌ فَأَتَيْتُ خَدِيجَةَ فَقُلْتُ دَثِّرُونِي فَدَثَّرُونِي فَصَبُّوا عَلَيَّ مَاءً فَأَنْزَلَ اللَّهُ عَزَّ وَجَلَّ { يَا أَيُّهَا الْمُدَّثِّرُ قُمْ فَأَنْذِرْ وَرَبَّكَ فَكَبِّرْ وَثِيَابَكَ فَطَهِّرْ }.[المدثر: 1-4]

Al-Awza'i said: "I heard Yahya say: 'I asked Abu Salamah: "What part of the Qur'an was revealed first?" He said: "O you enveloped in garments!" I said: Or: "Read!" He said: "I asked Jabir bin 'Abdullah: 'What part of the Qur'an was revealed first?' He said: "O you enveloped in garments! I said: 'Or: "Read!"' Jabir said: 'I will tell you what the Messenger of Allah (s.a.w) told us. He said: "I stayed in Hira' for a month, and when my stay was over, I went down to the bottom of the valley and I heard my name called. I looked in front of me and behind me, and to my right and my left, and I did not see anyone. Then I heard my name called (again). I looked and I did not see anyone. Then my name was called again and I raised my head, and there he was on a throne in the air" - meaning Jibril, - "I started to tremble violently when I saw him, and I went to Khadijah and said: 'Cover me', and they covered me and poured water on me.' Then Allah revealed: "O you enveloped in garments! Arise and warn! And magnify your Lord! And purify your garments!."