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."' (JA)
English reference (JA): Vol. 3, Book 11, Hadith 2092 (JA)
Arabic reference (JA): Book 11, Hadith 2170 (JA)