[Machine] The Messenger of Allah ﷺ did not used to pray the night prayer sitting until he became old. He used to recite while sitting, and when he wanted to bow, he stood up and recited about thirty or forty verses, then he bowed.  

لَمْ تَرَ رَسُولَ اللهِ ﷺ يُصَلِّي صَلَاةَ اللَّيْلِ قَاعِدًا قَطُّ حَتَّى أَسَنَّ فَكَانَ يَقْرَأُ قَاعِدًا حَتَّى إِذَا أَرَادَ أَنْ يَرْكَعَ قَامَ فَقَرَأَ نَحْوًا مِنْ ثَلَاثِينَ أَوْ أَرْبَعِينَ آيَةً ثُمَّ رَكَعَ  

when the prophet ﷺ prayed sitting, he recited the Quran in sitting condition. When the amount of his recitation remained about thirty or forty verses he stood up and recited them standing. He then bowed and prostrated and then did so in the second Rak’ah of the prayer. Abu Dawud said: 'Alqamah b. Waqqas narrated this tradition on the authority of 'Aishah from the Prophet ﷺ to the same effect. (Using translation from Abū Dāʾūd 954)   

رَسُولَ اللهِ ﷺ كَانَ يُصَلِّي جَالِسًا فَيَقْرَأُ وَهُوَ جَالِسٌ فَإِذَا بَقِيَ مِنْ قَرَاءَتِهِ قَدْرُ مَا يَكُونُ ثَلَاثِينَ أَوْ أَرْبَعِينَ آيَةً قَامَ فَقَرَأَ وَهُوَ قَائِمٌ ثُمَّ رَكَعَ ثُمَّ سَجَدَ ثُمَّ يَفْعَلُ فِي الرَّكْعَةِ الثَّانِيَةِ مِثْلَ ذَلِكَ  

[Machine] The Prophet ﷺ used to recite (the Qur'an) while sitting and when he wanted to perform the rukoo (bowing), he would stand up after reciting about forty verses.  

النَّبِيَّ ﷺ كَانَ يَقْرَأُ وَهُوَ قَاعِدٌ فَإِذَا أَرَادَ أَنْ يَرْكَعَ قَامَ قَدْرَ مَا يَقْرَأُ إِنْسَانٌ أَرْبَعِينَ آيَةً