Sahih Bukhari Volume 5, Book 64, Hadith 4204

حَدَّثَنَا مُوسَى بْنُ إِسْمَاعِيلَ، حَدَّثَنَا عَبْدُ الْوَاحِدِ، عَنْ عَاصِمٍ، عَنْ أَبِي عُثْمَانَ، عَنْ أَبِي مُوسَى الأَشْعَرِيِّ ـ رضى الله عنه ـ قَالَ لَمَّا غَزَا رَسُولُ اللَّهِ صلى الله عليه وسلم خَيْبَرَ ـ أَوْ قَالَ لَمَّا تَوَجَّهَ رَسُولُ اللَّهِ صلى الله عليه وسلم ـ أَشْرَفَ النَّاسُ عَلَى وَادٍ، فَرَفَعُوا أَصْوَاتَهُمْ بِالتَّكْبِيرِ اللَّهُ أَكْبَرُ اللَّهُ أَكْبَرُ، لاَ إِلَهَ إِلاَّ اللَّهُ‏.‏ فَقَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏"‏ ارْبَعُوا عَلَى أَنْفُسِكُمْ، إِنَّكُمْ لاَ تَدْعُونَ أَصَمَّ وَلاَ غَائِبًا، إِنَّكُمْ تَدْعُونَ سَمِيعًا قَرِيبًا وَهْوَ مَعَكُمْ ‏"‏‏.‏ وَأَنَا خَلْفَ دَابَّةِ رَسُولِ اللَّهِ صلى الله عليه وسلم فَسَمِعَنِي وَأَنَا أَقُولُ لاَ حَوْلَ وَلاَ قُوَّةَ إِلاَّ بِاللَّهِ، فَقَالَ لِي ‏"‏ يَا عَبْدَ اللَّهِ بْنَ قَيْسٍ ‏"‏‏.‏ قُلْتُ لَبَّيْكَ رَسُولَ اللَّهِ‏.‏ قَالَ ‏"‏ أَلاَ أَدُلُّكَ عَلَى كَلِمَةٍ مِنْ كَنْزٍ مِنْ كُنُوزِ الْجَنَّةِ ‏"‏‏.‏ قُلْتُ بَلَى يَا رَسُولَ اللَّهِ فِدَاكَ أَبِي وَأُمِّي‏.‏ قَالَ ‏"‏ لاَ حَوْلَ وَلاَ قُوَّةَ إِلاَّ بِاللَّهِ ‏"‏‏

Narrated By Abu Musa Al-Ashari : 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."