I spent a night with my maternal aunt Maymunah. The Prophet ﷺ got up to pray at night. He prayed thirteen rak'ahs including two rak'ahs of the dawn prayer. I guessed that he stood in every rak'ah as long as one could recite Surah al-Muzzammil (73).  

بِتُّ عِنْدَ خَالَتِي مَيْمُونَةَ فَقَامَ النَّبِيُّ ﷺ يُصَلِّي مِنَ اللَّيْلِ فَصَلَّى ثَلاَثَ عَشْرَةَ رَكْعَةً مِنْهَا رَكْعَتَا الْفَجْرِ حَزَرْتُ قِيَامَهُ فِي كُلِّ رَكْعَةٍ بِقَدْرِ { يَا أَيُّهَا الْمُزَّمِّلُ } لَمْ يَقُلْ نُوحٌ مِنْهَا رَكْعَتَا الْفَجْرِ  

[Machine] I was at the house of Maymuna, and the Prophet ﷺ stood up to pray at night. I joined him on his left side, and he held my hand, placing me on his right. Then he prayed thirteen rak'ahs, and I estimated the length of his standing in each rak'ah, saying, "O you, wrapped in garments!"  

كُنْتُ فِي بَيْتِ مَيْمُونَةَ فَقَامَ النَّبِيُّ ﷺ يُصَلِّي مِنَ اللَّيْلِ فَقُمْتُ مَعَهُ عَلَى يَسَارِهِ فَأَخَذَ بِيَدِي فَجَعَلَنِي عَنْ يَمِينِهِ ثُمَّ صَلَّى ثَلَاثَ عَشْرَةَ رَكْعَةً حَزَرْتُ قَدْرَ قِيَامِهِ فِي كُلِّ رَكْعَةٍ قَدْرَ يَا أَيُّهَا الْمُزَّمِّلُ  

[Machine] I was at my aunt Maymuna's house. The Prophet ﷺ got up to pray at night, so I stood to his left. He took my hand and placed me on his right. Then he prayed thirteen units of prayer. I observed his standing in each unit just as O' Enveloped One.  

كُنْتُ فِي بَيْتِ خَالَتِي مَيْمُونَةَ «فَقَامَ النَّبِيُّ ﷺ يُصَلِّي مِنَ اللَّيْلِ فَقُمْتُ عَنْ يَسَارِهِ فَأَخَذَ بِيَدِي فَجَعَلَنِي عَنْ يَمِينِهِ ثُمَّ صَلَّى ثَلَاثَ عَشْرَةَ رَكْعَةً حَرَزْتُ قِيَامَهُ فِي كُلِّ رَكْعَةٍ قَدْرَ يَا أَيُّهَا الْمُزَّمِّلُ»  

[Machine] I stayed at the house of Maymuna, so the Prophet ﷺ got up to pray in the night. I stood on his left side and he held my hand and placed me on his right. Then he prayed thirteen rak'ahs, and I estimated the amount of time he stood in each rak'ah. In each rak'ah he recited, "O you wrapped in garments" [Surah Al-Muzzammil, verse 1].  

بِتُّ فِي بَيْتِ مَيْمُونَةَ فَقَامَ النَّبِيُّ ﷺ يُصَلِّي مِنَ اللَّيْلِ فَقُمْتُ مَعَهُ عَنْ يَسَارِهِ فَأَخَذَ بِيَدِي فَجَعَلَنِي عَنْ يَمِينِهِ ثُمَّ صَلَّى ثَلَاثَ عَشْرَةَ رَكْعَةً حَزَرْتُ قَدْرَ قِيَامِهِ فِي كُلِّ رَكْعَةٍ {يَا أَيُّهَا الْمُزَّمِّلُ} [المزمل 1]  

I spent a night with my maternal aunt Maymunah. The Prophet ﷺ got up to pray at night. He prayed thirteen rak'ahs including two rak'ahs of the dawn prayer. I guessed that he stood in every rak'ah as long as one could recite Surah al-Muzzammil (73). (Using translation from Abū Dāʾūd 1365)   

بِتُّ عِنْدَ خَالَتِي مَيْمُونَةَ فَقَامَ النَّبِيُّ ﷺ يُصَلِّي مِنَ اللَّيْلِ فَصَلَّى ثَلَاثَ عَشْرَةَ رَكْعَةً مِنْهَا رَكْعَتَا الْفَجْرِ حَزَرْتُ قِيَامَهُ فِي كُلِّ رَكْعَةٍ بِقَدْرِ يَا أَيُّهَا الْمُزَّمِّلُ لَمْ يَقُلْ نُوحٌ مِنْهَا رَكْعَتَا الْفَجْرِ  

"كُنْتُ فِى بَيْتِ مَيْمُونَةَ، فَقَامَ النَّبِىُّ ﷺ يُصَلِّى مِنَ اللَّيْلِ، فَقُمْتُ مَعَهُ عَلَى يَسَارهِ، فَأَخَذَ بيَدى فَجَعَلَنى عَنْ يَمينهِ، ثُمَّ صَلَّى ثَلاثَ عَشْرَةَ رَكْعَةً، حَزَرْتُ قيَامَهُ في كُلِّ ركْعَةٍ قَدْرَ {يأَيُّهَا الْمُزَّمِّلُ} ".  

"كُنْتُ فِى بَيْتِ مَيْمُونَةَ فَقَامَ النَّبِيُّ ﷺ مِنَ الَّليْلِ، فَقُمْتُ مَعَهُ عَلَى يَسَارِهِ، فَأَخَذَ بِيَدِى، فَجَعَلَنِى عَنْ يَمِينِهِ، ثُمَّ صَلَّى ثَلاَثَ عَشْرَةَ رَكْعَةً، حَزَرْتُ (*) قِيَامَهُ فِى كُلِّ رَكْعَةٍ قَدْرَ: يَا أَيُّهَا الْمُزَّمِّلُ".