Sunan Ibn Majah, Book 5, Hadith 1216 (In-Book) ⓘ
It was narrated that ‘Asim bin Damrah As-Saluli said: “We asked ‘Ali about the voluntary (prayer) of Allah’s Messenger during the day. He said: ‘You will not be able.’ We said: ‘Inform us of it, we will do what we can of it?’ So he said: ‘When he prayed the Fajr he would delay praying any more. When the sun appeared over there (west) – like it appears here, meaning in the direction of the east, about the amount for the ‘Asr prayer from there, meaning in the direction of the west, meaning before the Maghrib – he would stand and perform two Rak’ah* then he would delay praying until the sun appeared over there (west), meaning in the direction of the east, about the amount of the Zuhr prayer from there, then he would stand and perform four. And, four before the Zuhr when the sun passed the zenith, and two Rak’ah after it, and, four before the ‘Asr, separating between every two Rak’ah with Taslim** upon the angels that are close (to Allah), the Prophets, and those who follow them among the Muslims and the believers.’” 'Ali said: "That is sixteen Rak'ah of voluntary prayer which Allah's Messenger performed during the day. And there are very few who offer them regularly." Waki` said: “My father added: Habib bin Abu Thabit said: ‘O Abu Ishaq, this mosque filled with gold would not be dearer to me than this Hadith of yours.’”
حَدَّثَنَا عَلِيُّ بْنُ مُحَمَّدٍ، حَدَّثَنَا وَكِيعٌ، حَدَّثَنَا سُفْيَانُ، وَأَبِي، وَإِسْرَائِيلُ، عَنْ أَبِي إِسْحَاقَ، عَنْ عَاصِمِ بْنِ ضَمْرَةَ السَّلُولِيِّ، قَالَ سَأَلْنَا عَلِيًّا عَنْ تَطَوُّعِ، رَسُولِ اللَّهِ ـ صلى الله عليه وسلم ـ بِالنَّهَارِ فَقَالَ إِنَّكُمْ لاَ تُطِيقُونَهُ فَقُلْنَا أَخْبِرْنَا بِهِ نَأْخُذْ مِنْهُ مَا اسْتَطَعْنَا . قَالَ كَانَ رَسُولُ اللَّهِ ـ صلى الله عليه وسلم ـ إِذَا صَلَّى الْفَجْرَ يُمْهِلُ حَتَّى إِذَا كَانَتِ الشَّمْسُ مِنْ هَاهُنَا - يَعْنِي مِنْ قِبَلِ الْمَشْرِقِ - بِمِقْدَارِهَا مِنْ صَلاَةِ الْعَصْرِ مِنْ هَا هُنَا - يَعْنِي مِنْ قِبَلِ الْمَغْرِبِ - قَامَ فَصَلَّى رَكْعَتَيْنِ ثُمَّ يُمْهِلُ حَتَّى إِذَا كَانَتِ الشَّمْسُ مِنْ هَا هُنَا - يَعْنِي مِنْ قِبَلِ الْمَشْرِقِ - مِقْدَارَهَا مِنْ صَلاَةِ الظُّهْرِ مِنْ هَا هُنَا قَامَ فَصَلَّى أَرْبَعًا وَأَرْبَعًا قَبْلَ الظُّهْرِ إِذَا زَالَتِ الشَّمْسُ وَرَكْعَتَيْنِ بَعْدَهَا وَأَرْبَعًا قَبْلَ الْعَصْرِ يَفْصِلُ بَيْنَ كُلِّ رَكْعَتَيْنِ بِالتَّسْلِيمِ عَلَى الْمَلاَئِكَةِ الْمُقَرَّبِينَ وَالنَّبِيِّينَ وَمَنْ تَبِعَهُمْ مِنَ الْمُسْلِمِينَ وَالْمُؤْمِنِينَ . قَالَ عَلِيٌّ فَتِلْكَ سِتَّ عَشْرَةَ رَكْعَةً تَطَوُّعُ رَسُولِ اللَّهِ ـ صلى الله عليه وسلم ـ بِالنَّهَارِ وَقَلَّ مَنْ يُدَاوِمُ عَلَيْهَا . قَالَ وَكِيعٌ زَادَ فِيهِ أَبِي فَقَالَ حَبِيبُ بْنُ أَبِي ثَابِتٍ يَا أَبَا إِسْحَاقَ مَا أُحِبُّ أَنَّ لِي بِحَدِيثِكَ هَذَا مِلْءَ مَسْجِدِكَ هَذَا ذَهَبًا .
also referenced under: Hadith 1161 (Reference) & Volume 2, Book 5, Hadith 1161 (DarusSalam)