Sunan Ibn Majah 614

It was narrated that 'Abdullah bin Harith bin Nawfal said:"I asked whether the Messenger of Allah prayed voluntary prayer when traveling, but I could not find anyone to tell me until Umm Hani' bint Abu Talib told me that he had come during the year of the Conquest (of Makkah). He ordered that a screen be held up, and that was done, and he took a bath; then he prayed eight Rak'ah (units) of voluntary prayer