It was narrated from Salim that his father said:
"The swearing most frequently sworn by the Messenger of Allah (ﷺ) was: 'No, by the Controller of the hearts."' (RU)
English reference (RU): Vol. 3, Book 11, Hadith 2092 (RU)
Arabic reference (RU): Book 11, Hadith 2170 (RU)