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
Sahih Muslim 2704 f

Abu Musa, reported. We were along with Allah's Messenger (ﷺ) in an expedition. The rest of the hadith is the same (and there is an addi- tion of these words in that):

" He (the Holy Prophet) said: He Whom you are sup- plicating is nearer to every one of you than the neck of his camel." And there is no mention of these words:" There is no might and no power but that of Allah."
وَحَدَّثَنَا إِسْحَاقُ بْنُ إِبْرَاهِيمَ، أَخْبَرَنَا الثَّقَفِيُّ، حَدَّثَنَا خَالِدٌ الْحَذَّاءُ، عَنْ أَبِي عُثْمَانَ، عَنْ أَبِي مُوسَى، قَالَ كُنَّا مَعَ رَسُولِ اللَّهِ صلى الله عليه وسلم فِي غَزَاةٍ ‏.‏ فَذَكَرَ الْحَدِيثَ وَقَالَ فِيهِ ‏ "‏ وَالَّذِي تَدْعُونَهُ أَقْرَبُ إِلَى أَحَدِكُمْ مِنْ عُنُقِ رَاحِلَةِ أَحَدِكُمْ ‏"‏ ‏.‏ وَلَيْسَ فِي حَدِيثِهِ ذِكْرُ لاَ حَوْلَ وَلاَ قُوَّةَ إِلاَّ بِاللَّهِ ‏.‏
Reference : Sahih Muslim 2704f
In-book reference : Book 48, Hadith 61
USC-MSA web (English) reference : Book 35, Hadith 6531
  (deprecated numbering scheme)