It is narrated from Sayyiduna Amir bin Rabi’ah (may Allah be pleased with him) that he saw the Messenger of Allah (peace and blessings of Allah be upon him) performing voluntary prayers at night while traveling on his mount, regardless of which direction the mount was facing (even if it was not facing the Ka’bah).

Narrated Abdullah bin Abbas (may Allah be pleased with both of them): When the Messenger of Allah (peace and blessings of Allah be upon him) was traveling, he would combine the Zuhr and Asr prayers, and he would also combine and perform the Maghrib and Isha prayers together.

Sayyiduna Imran bin Husain (may Allah be pleased with him) says: I had hemorrhoids, so I asked the Messenger of Allah (peace and blessings of Allah be upon him) about prayer—whether it is permissible to pray while sitting. He (peace and blessings of Allah be upon him) said: "Pray standing, and if you are not able, then sitting, and if you are not able to sit, then lie on your side and pray."

Umm al-Mu'mineen Aisha Siddiqa (may Allah be pleased with her) says that she never saw the Messenger of Allah (peace and blessings be upon him) performing the Tahajjud prayer sitting down, until when the Prophet (peace and blessings be upon him) became older, he would recite (Qur'an) while sitting, and then when he intended to bow (for ruku'), he would stand up and recite about thirty or forty verses and then perform ruku'.

Umm al-Mu'mineen Aisha Siddiqa (may Allah be pleased with her) says in a narration that he used to do the same in the second rak'ah as well. Then when the Prophet (peace be upon him) completed the prayer, he would see: if I was awake, he would talk with me, and if I was asleep, the Prophet (peace be upon him) would remain lying down.