كتاب الذكر والدعاء والتوبة والاستغفار
48
The Book Pertaining to the Remembrance of Allah, Supplication, Repentance and Seeking Forgiveness
(13)
Chapter: It Is Recommend To Lower One's Voice When Saying Remembrance, Except In The Cases Where It Is Commanded To Raise The Voice Such As The Talbiyah Etc. It Is Recommend To Say A Great Deal, "There Is No Power And No Strength Except With Allah"
(13)
باب اسْتِحْبَابِ خَفْضِ الصَّوْتِ بِالذِّكْرِ

Abu Musa Ash'ari reported that Allah's Messenger (ﷺ) said to him:

Should I not direct you to the words from the treasures of Paradise, or he said: Like a treasure from the treasures of Paradise? I said: Of course, do that. Thereupon he said:" There is no might and no power but that of Allah."
حَدَّثَنَا إِسْحَاقُ بْنُ إِبْرَاهِيمَ، أَخْبَرَنَا النَّضْرُ بْنُ شُمَيْلٍ، حَدَّثَنَا عُثْمَانُ، - وَهُوَ ابْنُ غِيَاثٍ - حَدَّثَنَا أَبُو عُثْمَانَ، عَنْ أَبِي مُوسَى الأَشْعَرِيِّ، قَالَ قَالَ لِي رَسُولُ اللَّهِ صلى الله عليه وسلم ‏"‏ أَلاَ أَدُلُّكَ عَلَى كَلِمَةٍ مِنْ كُنُوزِ الْجَنَّةِ - أَوْ قَالَ - عَلَى كَنْزٍ مِنْ كُنُوزِ الْجَنَّةِ ‏"‏ ‏.‏ فَقُلْتُ بَلَى ‏.‏ فَقَالَ ‏"‏ لاَ حَوْلَ وَلاَ قُوَّةَ إِلاَّ بِاللَّهِ ‏"‏ ‏.‏
Reference : Sahih Muslim 2704 g
In-book reference : Book 48, Hadith 62
USC-MSA web (English) reference : Book 35, Hadith 6532
  (deprecated numbering scheme)