It is narrated from Sayyiduna Salman al-Farisi (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "When a man is in a desolate land and the time of prayer comes, let him perform ablution (wudu); if he does not find water, let him perform tayammum. If he calls the iqamah, his two angels will pray with him; and if he calls both the adhan and the iqamah, so many of the armies of Allah will pray behind him that their two ends cannot be seen."
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 6095