(2) باب الْحَلِفِ بِمُصَرِّفِ الْقُلُوبِ
It was narrated from Salim that his father said:
"The oath by which the Messenger of Allah used to swear was: 'No, by the Controller of the hearts.'" (ID)
Reference (ID): Sunan an-Nasa'i 3762 (ID)
In-book reference (ID): Book 35, Hadith 2 (ID)
English translation (ID): Vol. 4, Book 35, Hadith 3793 (ID)