Yahya bin Abu Kathir reported,

I asked Abu Salama bin Abdul-Rahman about the first thing revealed of the Quran, and he said, "You who are wrapped in a cloak" [Muddaththir 74:1].I said, "But people say it was 'Recite in the name of your Lord who created' [Alaq 96:1]."Abu Salama replied, "I asked Jabir bin Abdullah about that, and I said to him just what you have said to me."Jabir said, "I will tell you nothing but what the Messenger of Allah ﷺ told us. He said, 'I had been staying in seclusion at Hira, and when I completed my stay I came down. Then I was called. I looked to my right and saw nothing, I looked to my left and saw nothing, I looked in front of me and saw nothing, and I looked behind me and saw nothing. Then I raised my head and saw something. So I went to Khadijah and said, "Wrap me up, and pour cold water over me." They wrapped me up and poured cold water over me, and then there was revealed, "You who are wrapped in a cloak, arise and warn, and magnify your Lord" [Muddaththir 74:1–3].'"

عن يحيى بن أبي كثير قال

سألت أبا سلمة بن عبد الرحمن، عن أول ما نزل من القرآن، قال: {يأيها المدثر} قلت: يقولون: {اقرأ باسم ربك الذي خلق} [العلق: ١] فقال أبو سلمة: سألت جابر بن عبد الله عن ذلك وقلت له مثل الذي قلت، فقال جابر: لا أحدثك إلا ما حدثنا رسول الله ﷺ قال: جاورت بحراء، فلما قضيت جواري هبطت، فنوديت، فنظرت عن يميني فلم أر شيئا، ونظرت عن شمالي فلم أر شيئا، ونظرت أمامي فلم أر شيئا، ونظرت خلفي فلم أر شيئا، فرفعت رأسي فرأيت شيئا، فأتيت خديجة، فقلت: دتروني، وصبوا علي ماء باردا، قال: فدتروني وصبوا علي ماء باردا، قال: فنزلت: {ياأيها المدثر قم فأنذر وربك فكبر}