It is narrated from Umm al-Mu'mineen Sayyidah Hafsah (may Allah be pleased with her) that I never saw the Messenger of Allah (peace and blessings be upon him) performing voluntary prayers sitting down, except for one year before his passing; during that time, he (peace be upon him) would perform voluntary prayers sitting and would recite the surah with such excellence and deliberation that it would seem very lengthy.

It is narrated from Umm al-Mu'minin Sayyida Aisha Siddiqa (may Allah be pleased with her) that she never saw the Messenger of Allah (peace and blessings be upon him) performing the Tahajjud prayer sitting, except when he became old, then he started to pray sitting. Whenever he would recite thirty or forty verses before bowing, he would recite them standing, then he would bow.

It is narrated from Sayyida Aisha, may Allah be pleased with her, that when the Messenger of Allah, peace and blessings be upon him, would pray sitting, he would recite the Word of Allah while sitting. When thirty or forty verses remained, he would stand up and recite them, then perform bowing (ruku) and prostration (sajda), and he would do the same in the second rak'ah.

It reached Imam Malik, may Allah have mercy on him, from Hazrat Urwah bin Zubair and Hazrat Saeed bin Musayyib that they used to perform voluntary prayers sitting, with both feet upright and their buttocks touching the ground.