Ahmad ibn Muhammad, from al-Abbas ibn Ma'ruf, from Safwan ibn Yahya, from Abdillah ibn Maskan and Muhammad ibn al-Nu'man al-Ahwal, from Abu Abdillah عليه السلام, peace be upon him, who said: Imam al-Sadiq عليه السلام said: “When a traveller joins a group of residents in their prayer, then if it is the noon prayer (‘al-ula’), he should make the obligatory (prayer) in the first two rak‘ahs. And if it is the afternoon prayer (‘al-Asr’), he should make the first two (rak‘ahs) supererogatory (nafila) and the last two (rak’ahs) as obligatory (fardh).”