Sayyiduna Anas bin Malik (may Allah be pleased with him) narrates: The Prophet Muhammad (peace and blessings be upon him) heard a man during a journey who was saying «الله اکبر»«اللہ اکبر» (i.e., he was giving the call to prayer). The Prophet Muhammad (peace and blessings be upon him) said: "This is upon the natural disposition (fitrah)." Then he said: «الشهد ان لا اله الا اللہ», so the Prophet Muhammad (peace and blessings be upon him) said: "The Hellfire has become forbidden for him." We hurried to this man and found that he was a shepherd of animals, and when the time for prayer came, he was giving the call to prayer for it.
Hadith Referenceصحیح ابن حبان / كتاب الصلاة / 1665
Hadith Gradingفضيلة الشيخ الإمام محمد ناصر الدين الألبانيصحيح - «صحيح أبي داود» (2368): م.فضيلة الشيخ العلّامة شُعيب الأرناؤوطإسناده صحيح، حسين بن معاذ بن خليف: ثقة، روى له أبو داود، وباقي رجال السند على شرطهما.