Sahih Muslim 2704 a
Abu Musa reported:
We were along with Allah's Apostle (ﷺ) on a journey when the people began to pronounce "Allahu Akbar" in a loud voice. Thereupon Allah's Messenger (ﷺ) said: O people, show mercy to yourselves for you are not calling One who is deaf or absent. Verily, you are calling One who is All-Hearing (and) Near to you and is with you. Abu Musa said that he had been behind him (the Prophet) and reciting: "There is neither might nor power but that of Allah." He (the Prophet), while addressing 'Abdullah b. Qais, said: Should I not direct you to a treasure from amongst the treasures of Paradise? I ('Abdullah b. Qais) said: Allah's Messenger, do it, of course. Thereupon he (the Prophet) said: Then recite: "There is no might and no power but that of Allah."
حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا مُحَمَّدُ بْنُ فُضَيْلٍ، وَأَبُو مُعَاوِيَةَ عَنْ عَاصِمٍ،
 عَنْ أَبِي عُثْمَانَ، عَنْ أَبِي مُوسَى، قَالَ كُنَّا مَعَ النَّبِيِّ صلى الله عليه وسلم فِي سَفَرٍ فَجَعَلَ
 النَّاسُ يَجْهَرُونَ بِالتَّكْبِيرِ فَقَالَ النَّبِيُّ صلى الله عليه وسلم ‏"‏ أَيُّهَا النَّاسُ ارْبَعُوا عَلَى
 أَنْفُسِكُمْ إِنَّكُمْ لَيْسَ تَدْعُونَ أَصَمَّ وَلاَ غَائِبًا إِنَّكُمْ تَدْعُونَ سَمِيعًا قَرِيبًا وَهُوَ مَعَكُمْ ‏"‏ ‏.‏ قَالَ
 وَأَنَا خَلْفَهُ وَأَنَا أَقُولُ لاَ حَوْلَ وَلاَ قُوَّةَ إِلاَّ بِاللَّهِ فَقَالَ ‏"‏ يَا عَبْدَ اللَّهِ بْنَ قَيْسٍ أَلاَ أَدُلُّكَ
 عَلَى كَنْزٍ مِنْ كُنُوزِ الْجَنَّةِ ‏"‏ ‏.‏ فَقُلْتُ بَلَى يَا رَسُولَ اللَّهِ ‏.‏ قَالَ ‏"‏ قُلْ لاَ حَوْلَ وَلاَ قُوَّةَ إِلاَّ
 بِاللَّهِ ‏"‏ ‏.‏