Hadithcore
Sahih Muslim, 175
sahih

It is narrated on the authority of Abu Huraira that the (words of Allah):

" And certainly he saw him in another descent" (al-Qur'an, Iiii. 13) imply that he saw Gabriel.

حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا عَلِيُّ بْنُ مُسْهِرٍ، عَنْ عَبْدِ الْمَلِكِ، عَنْ عَطَاءٍ، عَنْ أَبِي هُرَيْرَةَ، ‏{‏ وَلَقَدْ رَآهُ نَزْلَةً أُخْرَى‏}‏ قَالَ رَأَى جِبْرِيلَ ‏.‏

References2 variants
In-Book Reference
Book 1, Hadith 340
USC-MSA web (English) reference
Book 1, Hadith 333 (deprecated numbering scheme)
Sharh · explanationclick to expand
The journey of the Isra and Mi’raj was one of the miracles with which Allah supported His Prophet Muhammad (ﷺ). He honored and ascended him with Gabriel, the Angel, to the highest heavens so he saw Paradise along with His greatest signs. In this hadith, Abu Hurairah interpreted Allah's saying, "And he certainly saw him in another descent." (An-Najm: 13) and said that was the second time the Prophet saw Gabriel, the Angel, in his real form. The first time was at the beginning of his prophethood when Gabriel filled the sky's horizon, so he did not mean he saw his God. Some scholars think he saw his God with his heart, not his eyes, based on a hadith in Sahih Muslim reported by Ibn Abbas. They said that Allah granted his heart a sight so that he could see Him with his heart as if he saw Him with his eyes. It was also said that Allah firmed his heart so he could realize what he would see with his eyes. It was narrated in Sahih Muslim that Abu Dharr said, "I asked the Prophet (ﷺ), 'Have you seen your God?' The Prophet said, 'I saw a light.'" This Prophetic expression may mean that he saw Allah's light or another light that prevented him from seeing Allah, as in another Muslim narration in which Abu Dharr reported that the Prophet said, "A light. How can see Him?!" He meant that he saw a veil of light prevented him from seeing Allah. The Companions and the scholars after them differed on that. Some confirmed it while others negated it. It was said that it is most likely that he saw his God, but they differed on how he saw Him. Some confirmed it was with heart while others confirmed it was with eyes..