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 d

This hadith has been transmitted on the authority of Abu Musa with a slight variation of wording.

وَحَدَّثَنَاهُ مُحَمَّدُ بْنُ عَبْدِ الأَعْلَى، حَدَّثَنَا الْمُعْتَمِرُ، عَنْ أَبِيهِ، حَدَّثَنَا أَبُو عُثْمَانَ، عَنْ أَبِي مُوسَى، قَالَ بَيْنَمَا رَسُولُ اللَّهِ صلى الله عليه وسلم فَذَكَرَ نَحْوَهُ ‏.‏
Reference : Sahih Muslim 2704d
In-book reference : Book 48, Hadith 59
USC-MSA web (English) reference : Book 35, Hadith 6529
  (deprecated numbering scheme)