Musnad Ahmad 1375
It was narrated that Abu Ishaq said:
I heard `Asim bin Damrah say: We asked ‘Ali (رضي الله عنه) about the prayer of the Messenger of Allah (ﷺ) during the day and he said: You cannot do that. We said: Whoever among us is able to do it [will do it]. He said: When the sun was as high there as it is there the time of ‘Asr, he prayed two rak`ahs, When the sun was as high there as it is there at the time of Zuhr, he prayed four rak’ahs. He prayed four rak`ahs before Zuhr and two afterwards, and [he prayed] four rakʻahs before ‘Asr, separating each two rak`ahs with the greeting (tasleem) upon the angels who are close to Allah, the Prophets, and those who follow them of the believers and the Muslims.
حَدَّثَنَا مُحَمَّدُ بْنُ جَعْفَرٍ، حَدَّثَنَا شُعْبَةُ، عَنْ أَبِي إِسْحَاقَ، قَالَ سَمِعْتُ عَاصِمَ بْنَ ضَمْرَةَ، يَقُولُ سَأَلْنَا عَلِيًّا رَضِيَ اللَّهُ عَنْهُ عَنْ صَلَاةِ رَسُولِ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ مِنْ النَّهَارِ فَقَالَ إِنَّكُمْ لَا تُطِيقُونَ ذَلِكَ قُلْنَا مَنْ أَطَاقَ مِنَّا ذَلِكَ قَالَ إِذَا كَانَتْ الشَّمْسُ مِنْ هَاهُنَا كَهَيْئَتِهَا مِنْ هَاهُنَا عِنْدَ الْعَصْرِ صَلَّى رَكْعَتَيْنِ وَإِذَا كَانَتْ الشَّمْسُ مِنْ هَاهُنَا كَهَيْئَتِهَا مِنْ هَاهُنَا عِنْدَ الظُّهْرِ صَلَّى أَرْبَعًا وَيُصَلِّي قَبْلَ الظُّهْرِ أَرْبَعًا وَبَعْدَهَا رَكْعَتَيْنِ وَقَبْلَ الْعَصْرِ أَرْبَعًا وَيَفْصِلُ بَيْنَ كُلِّ رَكْعَتَيْنِ بِالتَّسْلِيمِ عَلَى الْمَلَائِكَةِ الْمُقَرَّبِينَ وَالنَّبِيِّينَ وَمَنْ تَبِعَهُمْ مِنْ الْمُؤْمِنِينَ وَالْمُسْلِمِينَ‏.‏