Prayer (Kitab Al-Salat): Detailed Rules of Law about the Prayer during Journey
Dawud :: Book 4 : Hadith 1199
Narrated Uqbah ibn Amir:
I heard the Apostle of Allah (peace_be_upon_him) say: Allah is pleased with a shepherd of goats who calls to prayer at the peak of a mountain, and offers prayer, Allah, the Exalted, says: Look at this servant of Mine; he calls to prayer and offers it and he fears Me. So I forgive him and admit him to paradise.