Musannaf Ibn Abi Shayba 3:5844

Abu Bakr narrated to us, he said: Mu'tamir ibn Sulayman narrated to us, from Layth, from Tawus, from Aisha, she said: "When you place the provision bag and the water skin, pray four [rak'ahs]." And when Tawus would arrive in Mecca, he would pray four [rak'ahs].