Musannaf Ibn Abi Shayba 2:159

Abu al-Ahwas narrated to us, from Abu Ishaq, from Asim ibn Damra, who said: Ali said: "Whichever man goes out to a land, and the prayer time arrives, let him choose the best and cleanest of the spots, for every spot loves that Allah be remembered upon it. If he wishes, he may call the adhan and the iqamah, and if he wishes, he may perform one iqamah and pray."