What important principle did the Prophet Muhammad (peace be upon him) emphasize to the people when they passed a high place overlooking a valley?
 Narrated Abu Musa Al-Ash`ari:                     When Allah's Apostle fought the battle of Khaibar, or when Allah's Apostle went towards it, (whenever) the people, (passed over a high place overlooking a valley, they raised their voices saying, "Allahu-Akbar! Allahu-Akbar! None has the right to be worshipped except Allah." On that Allah's Apostle said (to them), "Lower your voices, for you are not calling a deaf or an absent one, but you are calling a Hearer Who is near and is with you." I was behind the riding animal of Allah's Apostle and he heard me saying. "There Is neither might, nor power but with Allah," On that he said to me, "O `Abdullah bin Qais!" I said, "Labbaik. O Allah's Apostle!" He said, "Shall I tell you a sentence which is one of the treasures of Paradise" I said, "Yes, O Allah's Apostle! Let my father and mother be sacrificed for your sake." He said, "It is: There is neither might nor power but with Allah."