I fell ill in Persia and therefore, prayed in a sitting posture, and I asked 'A'isha about it and she said: The Messenger of Allah ﷺ prayed for a long time in the night sitting.
كُنْتُ شَاكِيًا بِفَارِسَ فَكُنْتُ أُصَلِّي قَاعِدًا فَسَأَلْتُ عَنْ ذَلِكَ عَائِشَةَ فَقَالَتْ كَانَ رَسُولُ اللَّهِ ﷺ يُصَلِّي لَيْلاً طَوِيلاً قَائِمًا فَذَكَرَ الْحَدِيثَ
[Machine] "I used to complain to Fares about being seated during prayer, so I asked Aisha about it. She said that the Messenger of Allah ﷺ used to pray during the night, either standing for a long time or sitting for a long time. When he recited while standing, he would either perform prostrations or show humility while standing. And when he recited while sitting, he would perform prostrations while sitting as well."
كُنْتُ شَاكِيًا بِفَارِسَ فَكُنْتُ أُصَلِّي قَاعِدًا فَسَأَلْتُ عَنْ ذَلِكَ عَائِشَةَ فَقَالَتْ كَانَ رَسُولُ اللهِ ﷺ يُصَلِّي لَيْلًا طَوِيلًا قَائِمًا وَلَيْلًا طَوِيلًا قَاعِدًا فَإِذَا قَرَأَ قَائِمًا رَكَعَ أَوْ خَشَعَ قَائِمًا وَإِذَا قَرَأَ قَاعِدًا رَكَعَ قَاعِدًا