The first thing the Messenger of Allah (may Allah's peace and blessings be upon him) started to experience from the revelation was the good vision in his sleep

عَنْ عَائِشَةَ أُمِّ المُؤْمِنِينَ رَضِيَ اللَّهُ عَنْها أَنَّهَا قَالَتْ: أَوَّلُ مَا بُدِئَ بِهِ رَسُولُ اللَّهِ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ مِنَ الوَحْيِ الرُّؤْيَا الصَّالِحَةُ فِي النَّوْمِ، فَكَانَ لاَ يَرَى رُؤْيَا إِلَّا جَاءَتْ مِثْلَ فَلَقِ الصُّبْحِ، ثُمَّ حُبِّبَ إِلَيْهِ الخَلاَءُ، وَكَانَ يَخْلُو بِغَارِ حِرَاءٍ فَيَتَحَنَّثُ فِيهِ -وَهُوَ التَّعَبُّدُ- اللَّيَالِيَ ذَوَاتِ العَدَدِ قَبْلَ أَنْ يَنْزِعَ إِلَى أَهْلِهِ، وَيَتَزَوَّدُ لِذَلِكَ، ثُمَّ يَرْجِعُ إِلَى خَدِيجَةَ فَيَتَزَوَّدُ لِمِثْلِهَا، حَتَّى جَاءَهُ الحَقُّ وَهُوَ فِي غَارِ حِرَاءٍ، فَجَاءَهُ المَلَكُ فَقَالَ: اقْرَأْ، قَالَ: «مَا أَنَا بِقَارِئٍ» قَالَ: «فَأَخَذَنِي فَغَطَّنِي حَتَّى بَلَغَ مِنِّي الجَهْدَ ثُمَّ أَرْسَلَنِي، فَقَالَ: اقْرَأْ، قُلْتُ: مَا أَنَا بِقَارِئٍ، فَأَخَذَنِي فَغَطَّنِي الثَّانِيَةَ حَتَّى بَلَغَ مِنِّي الجَهْدَ ثُمَّ أَرْسَلَنِي، فَقَالَ: اقْرَأْ، فَقُلْتُ: مَا أَنَا بِقَارِئٍ، فَأَخَذَنِي فَغَطَّنِي الثَّالِثَةَ ثُمَّ أَرْسَلَنِي، فَقَالَ: {اقْرَأْ بِاسْمِ رَبِّكَ الَّذِي خَلَقَ خَلَقَ الإِنْسَانَ مِنْ عَلَقٍ اقْرَأْ وَرَبُّكَ الأَكْرَمُ}»، [العلق:1-3] فَرَجَعَ بِهَا رَسُولُ اللَّهِ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ يَرْجُفُ فُؤَادُهُ، فَدَخَلَ عَلَى خَدِيجَةَ بِنْتِ خُوَيْلِدٍ رَضِيَ اللَّهُ عَنْهَا، فَقَالَ: «زَمِّلُونِي، زَمِّلُونِي» فَزَمَّلُوهُ حَتَّى ذَهَبَ عَنْهُ الرَّوْعُ، فَقَالَ لِخَدِيجَةَ وَأَخْبَرَهَا الخَبَرَ: «لَقَدْ خَشِيتُ عَلَى نَفْسِي» فَقَالَتْ خَدِيجَةُ: كَلَّا وَاللَّهِ مَا يُخْزِيكَ اللَّهُ أَبَدًا، إِنَّكَ لَتَصِلُ الرَّحِمَ، وَتَحْمِلُ الكَلَّ، وَتَكْسِبُ المَعْدُومَ، وَتَقْرِي الضَّيْفَ، وَتُعِينُ عَلَى نَوَائِبِ الحَقِّ، فَانْطَلَقَتْ بِهِ خَدِيجَةُ حَتَّى أَتَتْ بِهِ وَرَقَةَ بْنَ نَوْفَلِ بْنِ أَسَدِ بْنِ عَبْدِ العُزَّى، ابْنَ عَمِّ خَدِيجَةَ، وَكَانَ امْرَأً تَنَصَّرَ فِي الجَاهِلِيَّةِ، وَكَانَ يَكْتُبُ الكِتَابَ العِبْرَانِيَّ، فَيَكْتُبُ مِنَ الإِنْجِيلِ بِالعِبْرَانِيَّةِ مَا شَاءَ اللَّهُ أَنْ يَكْتُبَ، وَكَانَ شَيْخًا كَبِيرًا قَدْ عَمِيَ، فَقَالَتْ لَهُ خَدِيجَةُ: يَا ابْنَ عَمِّ، اسْمَعْ مِنَ ابْنِ أَخِيكَ، فَقَالَ لَهُ وَرَقَةُ: يَا ابْنَ أَخِي، مَاذَا تَرَى؟ فَأَخْبَرَهُ رَسُولُ اللَّهِ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ خَبَرَ مَا رَأَى، فَقَالَ لَهُ وَرَقَةُ: هَذَا النَّامُوسُ الَّذِي نَزَّلَ اللَّهُ عَلَى مُوسَى، يَا لَيْتَنِي فِيهَا جَذَعًا، لَيْتَنِي أَكُونُ حَيًّا إِذْ يُخْرِجُكَ قَوْمُكَ، فَقَالَ رَسُولُ اللَّهِ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ: «أَوَ مُخْرِجِيَّ هُمْ؟»، قَالَ: نَعَمْ، لَمْ يَأْتِ رَجُلٌ قَطُّ بِمِثْلِ مَا جِئْتَ بِهِ إِلَّا عُودِيَ، وَإِنْ يُدْرِكْنِي يَوْمُكَ أَنْصُرْكَ نَصْرًا مُؤَزَّرًا. ثُمَّ لَمْ يَنْشَبْ وَرَقَةُ أَنْ تُوُفِّيَ، وَفَتَرَ الوَحْيُ.

‘Ā’ishah, Mother of the Believers, (may Allah be pleased with her) reported: The first thing the Messenger of Allah (may Allah's peace and blessings be upon him) started to experience from the revelation was the good vision in his sleep. He never saw a vision except that it came true like the break of dawn. Then seclusion was endeared to him, and he used to retreat to the Cave of Hirā’, where he would engage in Tahannuth-which is worship—for several nights before returning to his family and taking provisions for this. He would then go back to Khadījah to take provisions again for a similar number of nights until the truth came to him while he was in the Cave of Hirā’. The Angel came to him and said: Read! He said: "I do not know how to read." He said: "He took hold of me and pressed me forcefully until I could no longer bear it and then released me, saying: Read! I said: I do not know how to read. He took hold of me and pressed me forcefully for the second time until I could no longer bear it and then released me, saying: Read! I said: I do not know how to read. He took hold of me and pressed me forcefully for the third time and then released me, saying: {Read in the name of your Lord Who created, created man from a clinging clot. Read, and your Lord is the Most Generous.}" [Surat al-‘Alaq: 1-3] The Messenger of Allah (may Allah's peace and blessings be upon him) returned with these while his heart was trembling. He entered upon Khadījah bint Khuwaylid (may Allah be pleased with her) and said: "Cover me! Cover me!" They covered him until the shock of fear was gone from him. Then he informed Khadījah of what had happened and said to her: "Indeed, I feared for myself." Khadījah said: No, by Allah, Allah will never fail you. Verily, you maintain kinship ties, help those in need, support the destitute, provide the guests with food and shelter, and assist those affected by calamities. Khadījah took him to her cousin Waraqah ibn Nawfal ibn Asad ibn ‘Abdul-‘Uzza, who had embraced Christianity in the pre-Islamic period and used to write the Scripture in Hebrew. He would write from the Gospel in Hebrew as much as Allah wished him to write. He was an old man and had lost his eyesight. Khadījah said to him: O my cousin, listen to what your nephew has to say. Waraqah said to him: O my nephew, what have you seen? The Messenger of Allah (may Allah's peace and blessings be upon him) informed him of what he had seen. Waraqah said to him: This is the same Nāmūs (i.e., the angel) whom Allah had sent to Moses. I wish I were young and could live until the time when your people would drive you out. The Messenger of Allah (may Allah's peace and blessings be upon him) said: "Would they drive me out?" Waraqah said: Yes. No one has ever come with something like what you have brought without being treated with hostility. If I should live until that day, I would support you strongly. Soon after, Waraqah passed away, and the revelation paused.

Source · Agreed upon

From the Hadith Encyclopedia (hadeethenc.com).