´It was narrated that ‘Abdullah bin Shaqiq Al-‘Uqaili said:` “I asked ‘Aishah about the prayer of the Messenger of Allah (ﷺ) at night. She said: ‘He used to pray for a long time at night standing up, and for a long time at night sitting down. If he prayed standing, he would bow standing, and if he prayed sitting, he would bow sitting.’”
Hadith Referenceسنن ابن ماجه / كتاب إقامة الصلاة والسنة / 1228
Hadith Gradingالألبانی:صحيح | زبیر علی زئی:صحيح مسلم
1؎: The point is that in supererogatory (nafl) prayers, there is complete flexibility: one may perform them sitting, or begin standing and then sit down, or begin sitting and then stand up.
Hafsa, daughter of 'Abdul Rahman bin Abu Bakr, reported that 'A'isha narrated to her that she and the Apostle of Allah (ﷺ) took a bath from the same vessel which contained water equal to three Mudds or thereabout.
Shaykh Maulana Abdul Aziz Alvi
Hadith Commentary:Benefits and Issues: One mudd (مد) of water amounts to two ratl, which is a quarter of a sa’ (صاع). In this way, the water will be slightly more than one liter, and in three mudd, the water will be less than three and a half liters. From this, it is understood that the Prophet (sallallahu alayhi wa sallam) sometimes managed with three mudd of water instead of three sa’ for ritual bath (ghusl), or in such a case, he may not have performed the ritual bath together (i.e., with someone else). Rather, due to the vessel being small, he would have performed the ritual bath one after the other. According to some, mudd here is in the meaning of sa’.
Source: Tuhfat al-Muslim: Commentary on Sahih Muslim, Page: 730
Aishah said: The Messenger of Allah ﷺ used to pray standing at night for a long time, and used to pray sitting at night for a long time. When he prayed standing, he bowed standing, and when he prayed sitting, he bowed sitting.
Shaykh Umar Farooq Saeedi
955. Commentary: The best practice is that when the recitation (qira’ah) is performed standing, then the bowing (ruku‘) should also be performed standing; and if the recitation is performed sitting, then the bowing should also be performed sitting... This, and the aforementioned scenario—i.e., if a portion of the rak‘ah is performed standing and a portion sitting—is also permissible.
Source: Sunan Abu Dawood – Commentary by Shaykh Umar Farooq Saeedi, Page: 955