Al-Mundhiri records in his book al-Targhib wal-Tarhib:

الترغيب في قراءة سورة الفاتحة وما جاء في فضلها

Encouragement to recite Surat al-Fatihah and what has been related of its virtues.

Source: al-Targhīb wal-Tarhīb 2/236

Abu Sa’id ibn al-Mu’alla reported: I was praying in the mosque when the Messenger of Allah, peace and blessings be upon him, called out to me but I did not respond. I said later, “O Messenger of Allah, I was praying.” The Prophet said:

أَلَمْ يَقُلْ اللَّهُ اسْتَجِيبُوا لِلَّهِ وَلِلرَّسُولِ إِذَا دَعَاكُمْ

Did not Allah say: Respond to Allah and the Messenger when he calls you? (8:24)

Then, the Prophet said:

أَلَا أُعَلِّمُكَ أَعْظَمَ سُورَةٍ فِي الْقُرْآنِ قَبْلَ أَنْ تَخْرُجَ مِنْ الْمَسْجِدِ

Shall I not teach you the greatest chapter in the Quran before you leave the mosque?

The Prophet took me by the hand and when he intended to leave, I said to him, “Did you not say that you would teach me the greatest chapter in the Quran?” The Prophet said:

الْحَمْدُ لِلَّهِ رَبِّ الْعَالَمِينَ هِيَ السَّبْعُ الْمَثَانِي وَالْقُرْآنُ الْعَظِيمُ الَّذِي أُوتِيتُهُ

All praise is due to Allah, the Lord of the worlds (1:1), which are the seven oft-repeated verses and the great Quran given to me.

Source: Ṣaḥīḥ al-Bukhārī 5006, Grade: Sahih

Ubayy ibn Ka’b reported: The Messenger of Allah, peace and blessings be upon him, said to him:

كَيْفَ تَقْرَأُ فِي الصَّلاَةِ

How do you recite in prayer?

Ubayy said, “I recite the foundation of the Book, Surat al-Fatihah.” The Prophet said:

وَالَّذِي نَفْسِي بِيَدِهِ مَا أُنْزِلَتْ فِي التَّوْرَاةِ وَلاَ فِي الْإِنْجِيلِ وَلاَ فِي الزَّبُورِ وَلاَ فِي الفُرْقَانِ مِثْلُهَا وَإِنَّهَا سَبْعٌ مِنَ الْمَثَانِي وَالقُرْآنُ الْعَظِيمُ الَّذِي أُعْطِيتُهُ

By the One in whose hand is my soul, nothing like it has been revealed in the Torah, nor the Gospel, nor the Psalms, nor the Furqan. Verily, they are the seven oft-repeated verses and the great Quran given to me.

Source: Sunan al-Tirmidhī 2875, Grade: Sahih

Anas ibn Malik reported: The Prophet, peace and blessings be upon him, was on a journey and he descended from his riding animal as a man among his companions was walking by his side. The Prophet turned to him and he said:

أَلَا أُخْبِرُكَ بِأَفْضَلِ الْقُرْآنِ

Shall I not tell you of the greatest of the Quran?

The Prophet recited to him:

الْحَمْدُ لِلَّهِ رَبِّ الْعَالَمِينَ يعني سورة الفاتحة

All praise is due to Allah, the Lord of the worlds,Surat al-Fatihah.

Source: Ṣaḥīḥ Ibn Ḥibbān 774, Grade: Sahih

Abu Huraira reported: The Messenger of Allah, peace and blessings be upon him, said:

قَالَ اللَّهُ تَعَالَى قَسَمْتُ الصَّلَاةَ بَيْنِي وَبَيْنَ عَبْدِي نِصْفَيْنِ وَلِعَبْدِي مَا سَأَلَ فَإِذَا قَالَ الْعَبْدُ الْحَمْدُ لِلَّهِ رَبِّ الْعَالَمِينَ قَالَ اللَّهُ تَعَالَى حَمِدَنِي عَبْدِي وَإِذَا قَالَ الرَّحْمَنِ الرَّحِيمِ قَالَ اللَّهُ تَعَالَى أَثْنَى عَلَيَّ عَبْدِي وَإِذَا قَالَ مَالِكِ يَوْمِ الدِّينِ قَالَ مَجَّدَنِي عَبْدِي وَقَالَ مَرَّةً فَوَّضَ إِلَيَّ عَبْدِي فَإِذَا قَالَ إِيَّاكَ نَعْبُدُ وَإِيَّاكَ نَسْتَعِينُ قَالَ هَذَا بَيْنِي وَبَيْنَ عَبْدِي وَلِعَبْدِي مَا سَأَلَ فَإِذَا قَالَ اهْدِنَا الصِّرَاطَ الْمُسْتَقِيمَ صِرَاطَ الَّذِينَ أَنْعَمْتَ عَلَيْهِمْ غَيْرِ الْمَغْضُوبِ عَلَيْهِمْ وَلَا الضَّالِّينَ قَالَ هَذَا لِعَبْدِي وَلِعَبْدِي مَا سَأَلَ

Allah Almighty said: I have divided prayer between Myself and My servant into two halves, and My servant shall have what he has asked for. When the servant says, ‘All praise is due to Allah the Lord of the worlds,’ Allah says: My servant has praised Me. When he says, ‘The Gracious, the Merciful,’ Allah says: My servant has exalted Me. When he says, ‘The Master of the Day of Judgment,’ Allah says: My servant has glorified Me and my servant has submitted to Me. When he says, ‘You alone we worship, You alone we ask for help,’ Allah says: This is between Me and My servant, and My servant will have what he has asked for. When he says, ‘Guide us to the straight path, the path of those whom you have favored, not those who went astray,’ Allah says: This is for My servant, and My servant will have what he has asked for.

Source: Ṣaḥīḥ Muslim 395, Grade: Sahih

Ibn Abbas reported: While the Angel Gabriel was sitting with the Prophet, peace and blessings be upon him, he heard a creaking noise above him. Gabriel raised his head and he said:

هَذَا بَابٌ مِنَ السَّمَاءِ فُتِحَ الْيَوْمَ لَمْ يُفْتَحْ قَطُّ إِلَّا الْيَوْمَ

This is a door of heaven that has been opened today and it has never been opened before today.

Then an angel descended from it, and Gabriel said:

هَذَا مَلَكٌ نَزَلَ إِلَى الْأَرْضِ لَمْ يَنْزِلْ قَطُّ إِلَّا الْيَوْمَ

This angel descended to the earth today and he has never descended until today.

The angel greeted him with peace and he said:

أَبْشِرْ بِنُورَيْنِ أُوتِيتَهُمَا لَمْ يُؤْتَهُمَا نَبِيٌّ قَبْلَكَ فَاتِحَةُ الْكِتَابِ يعني سورة الفاتحة وَخَوَاتِيمُ سُورَةِ الْبَقَرَةِ لَنْ تَقْرَأَ بِحَرْفٍ مِنْهُمَا إِلَّا أُعْطِيتَهُ

Rejoice in two lights you have been given, which were not given to any prophet before you: the opening of the Book, Surat al-Fatihah, and the last verses of Surat al-Baqarah. You will never recite a letter from them but that you will be given.

Source: Ṣaḥīḥ Muslim 806, Grade: Sahih