Sahih al-Bukhari, Book 65, Hadith 4777 (In-Book) ⓘ

Narrated Abu Huraira: One day while Allah's Messenger was sitting with the people, a man came to him walking and said, "O Allah's Messenger. What is Belief?" The Prophet said, "Belief is to believe in Allah, His Angels, His Books, His Apostles, and the meeting with Him, and to believe in the Resurrection." The man asked, "O Allah's Messenger What is Islam?" The Prophet replied, "Islam is to worship Allah and not worship anything besides Him, to offer prayers perfectly, to pay the (compulsory) charity i.e. Zakat and to fast the month of Ramadan." The man again asked, "O Allah's Messenger What is Ihsan (i.e. perfection or Benevolence)?" The Prophet said, "Ihsan is to worship Allah as if you see Him, and if you do not achieve this state of devotion, then (take it for granted that) Allah sees you." The man further asked, "O Allah's Messenger When will the Hour be established?" The Prophet replied, "The one who is asked about it does not know more than the questioner does, but I will describe to you its portents. When the lady slave gives birth to her mistress, that will be of its portents; when the bare-footed naked people become the chiefs of the people, that will be of its portents. The Hour is one of five things which nobody knows except Allah. Verily, the knowledge of the Hour is with Allah (alone). He sends down the rain, and knows that which is in the wombs." (31.34) Then the man left. The Prophet said, "Call him back to me." They went to call him back but could not see him. The Prophet said, "That was Gabriel who came to teach the people their religion." (See Hadith No. 47 Vol 1)

حَدَّثَنِي إِسْحَاقُ، عَنْ جَرِيرٍ، عَنْ أَبِي حَيَّانَ، عَنْ أَبِي زُرْعَةَ، عَنْ أَبِي هُرَيْرَةَ ـ رضى الله عنه ـ أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم كَانَ يَوْمًا بَارِزًا لِلنَّاسِ إِذْ أَتَاهُ رَجُلٌ يَمْشِي فَقَالَ يَا رَسُولَ اللَّهِ مَا الإِيمَانُ قَالَ ‏"‏ الإِيمَانُ أَنْ تُؤْمِنَ بِاللَّهِ وَمَلاَئِكَتِهِ وَرُسُلِهِ وَلِقَائِهِ وَتُؤْمِنَ بِالْبَعْثِ الآخِرِ ‏"‏‏.‏ قَالَ يَا رَسُولَ اللَّهِ مَا الإِسْلاَمُ قَالَ ‏"‏ الإِسْلاَمُ أَنْ تَعْبُدَ اللَّهَ وَلاَ تُشْرِكَ بِهِ شَيْئًا، وَتُقِيمَ الصَّلاَةَ، وَتُؤْتِيَ الزَّكَاةَ الْمَفْرُوضَةَ، وَتَصُومَ رَمَضَانَ ‏"‏‏.‏ قَالَ يَا رَسُولَ اللَّهِ، مَا الإِحْسَانُ قَالَ ‏"‏ الإِحْسَانُ أَنْ تَعْبُدَ اللَّهَ كَأَنَّكَ تَرَاهُ، فَإِنْ لَمْ تَكُنْ تَرَاهُ فَإِنَّهُ يَرَاكَ ‏"‏‏.‏ قَالَ يَا رَسُولَ اللَّهِ مَتَى السَّاعَةُ قَالَ ‏"‏ مَا الْمَسْئُولُ عَنْهَا بِأَعْلَمَ مِنَ السَّائِلِ، وَلَكِنْ سَأُحَدِّثُكَ عَنْ أَشْرَاطِهَا إِذَا وَلَدَتِ الْمَرْأَةُ رَبَّتَهَا، فَذَاكَ مِنْ أَشْرَاطِهَا، وَإِذَا كَانَ الْحُفَاةُ الْعُرَاةُ رُءُوسَ النَّاسِ فَذَاكَ مِنْ أَشْرَاطِهَا فِي خَمْسٍ لا يَعْلَمُهُنَّ إِلاَّ اللَّهُ ‏{‏إِنَّ اللَّهَ عِنْدَهُ عِلْمُ السَّاعَةِ وَيُنَزِّلُ الْغَيْثَ وَيَعْلَمُ مَا فِي الأَرْحَامِ‏}‏ ‏"‏‏.‏ ثُمَّ انْصَرَفَ الرَّجُلُ فَقَالَ ‏"‏ رُدُّوا عَلَىَّ ‏"‏‏.‏ فَأَخَذُوا لِيَرُدُّوا فَلَمْ يَرَوْا شَيْئًا‏.‏ فَقَالَ ‏"‏ هَذَا جِبْرِيلُ جَاءَ لِيُعَلِّمَ النَّاسَ دِينَهُمْ ‏"‏‏.‏