It is narrated from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) that we were with the Messenger of Allah (peace and blessings be upon him) on one of his journeys when suddenly we heard a caller saying: 'Allahu akbar, Allahu akbar' (Allah is the Greatest, Allah is the Greatest). The Messenger of Allah (peace and blessings be upon him) said: "He is upon the fitrah." He said: 'Ashhadu an la ilaha illallah' (I bear witness that there is no god but Allah). The Messenger of Allah (peace and blessings be upon him) said: "He has come out of the Fire." He said: We hurried towards him, and he was a man with livestock. The time of prayer had come, so he made the call.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 1904