Musannaf Ibn Abi Shayba 2:160

Mu'tamir ibn Sulayman narrated to us, from his father, from Abu 'Uthman, from Salman, who said: "There is no man in a land who performs ablution, and if he does not find water, he performs tayammum, then calls for the prayer, then establishes it, except that there are behind him from the soldiers of Allah those whose two ends cannot be seen."