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muslim:724a – ʿAmr al-Nāqid > ʿAbdah b. Sulaymān > Hishām b. ʿUrwah from his father > ʿĀʾishah

The Messenger of Allah ﷺ used to observe two rak'ahs of Sunnah (prayer) when he heard the Adhin and shortened them.  

مسلم:٧٢٤a – حَدَّثَنَا عَمْرٌو النَّاقِدُ حَدَّثَنَا عَبْدَةُ بْنُ سُلَيْمَانَ حَدَّثَنَا هِشَامُ بْنُ عُرْوَةَ عَنْ أَبِيهِ عَنْ عَائِشَةَ قَالَتْ

كَانَ رَسُولُ اللَّهِ ﷺ يُصَلِّي رَكْعَتَىِ الْفَجْرِ إِذَا سَمِعَ الأَذَانَ وَيُخَفِّفُهُمَا  

See similar narrations below:

Collected by Nasāʾī, Aḥmad, Ṭabarānī
nasai:1782 – Aḥmad b. Naṣr > ʿAmr b. Muḥammad > ʿAthhām b. ʿAlī > al-Aʿmash > Ḥabīb b. Abū Thābit > Saʿīd b. Jubayr > Ibn ʿAbbās

"The Prophet ﷺ used to pray two rak'ahs of Fajr when he heard the Adhan and he made them brief."  

النسائي:١٧٨٢ – أَخْبَرَنَا أَحْمَدُ بْنُ نَصْرٍ قَالَ حَدَّثَنَا عَمْرُو بْنُ مُحَمَّدٍ قَالَ حَدَّثَنَا عَثَّامُ بْنُ عَلِيٍّ قَالَ حَدَّثَنَا الأَعْمَشُ عَنْ حَبِيبِ بْنِ أَبِي ثَابِتٍ عَنْ سَعِيدِ بْنِ جُبَيْرٍ عَنِ ابْنِ عَبَّاسٍ قَالَ

كَانَ النَّبِيُّ ﷺ يُصَلِّي رَكْعَتَىِ الْفَجْرِ إِذَا سَمِعَ الأَذَانَ وَيُخَفِّفُهُمَا قَالَ أَبُو عَبْدِ الرَّحْمَنِ هَذَا حَدِيثٌ مُنْكَرٌ  

ahmad:25692 – Wakīʿ > Hishām b. ʿUrwah from his father > ʿĀʾishah

[Machine] The Prophet ﷺ used to shorten his two units of prayer during Fajr.  

أحمد:٢٥٦٩٢ – حَدَّثَنَا وَكِيعٌ قَالَ حَدَّثَنَا هِشَامُ بْنُ عُرْوَةَ عَنْ أَبِيهِ عَنْ عَائِشَةَ قَالَتْ

كَانَ النَّبِيُّ ﷺ يُخَفِّفُ رَكْعَتَيِ الْفَجْرِ  

tabarani:19726 – Abū al-Zinbāʿ > Yūsuf b. ʿAdī > al-Qāsim b. Mālik al-Madanī > Muḥammad b. Isḥāq > Nāfiʿ > Ibn ʿUmar > Ḥafṣah

[Machine] "That the Messenger of Allah, ﷺ , used to offer two units (rak'ahs) of the Fajr prayer in my house, and he used to shorten them."  

الطبراني:١٩٧٢٦ – حَدَّثَنَا أَبُو الزِّنْبَاعِ ثنا يُوسُفُ بْنُ عَدِيٍّ ثنا الْقَاسِمُ بْنُ مَالِكٍ الْمَدَنِيُّ عَنْ مُحَمَّدِ بْنِ إِسْحَاقَ عَنْ نَافِعٍ عَنِ ابْنِ عُمَرَ عَنْ حَفْصَةَ

«أَنَّ رَسُولَ اللهِ ﷺ صَلَّى رَكْعَتَيِ الْفَجْرِ فِي بَيْتِي وَكَانَ يُخَفِّفُهُمَا»