Sayyiduna Uqbah bin Amir (may Allah be pleased with him) said: I heard the Messenger of Allah (peace and blessings be upon him) say: "Your Lord is pleased with a shepherd who gives the call to prayer (adhan) and prays on the top of a mountain. Allah, the Mighty and Majestic, says: Look at this servant of Mine; he gives the call to prayer and establishes the prayer out of fear of Me. I have forgiven My servant and admitted him into Paradise."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 14904