Musannaf Ibn Abi Shaybah

Hazrat Hilal bin Yasaf says that sometimes I offer prayer while sitting; when I am about to perform ruku, I stand up, recite a little, and then perform ruku.

Hazrat Aisha (may Allah be pleased with her) narrates that the Messenger of Allah (peace and blessings be upon him) used to perform the Tahajjud prayer standing. When he grew older, he began to pray sitting. When thirty or forty verses remained, he would recite them standing and then perform prostration.

Hazrat Aisha (may Allah be pleased with her) narrates that the Noble Prophet (peace and blessings be upon him) used to perform prayer while sitting, and when about thirty or forty verses of a surah remained, he would stand up and recite them, then perform bowing (ruku).

Muhammad says that whoever recites (Qira'at) while sitting should also perform bowing (Ruku') and prostration (Sajda) while sitting, and whoever recites while standing should also perform bowing and prostration while standing. Hasan says that he has the choice to do as he wishes.