The oath the Messenger of Allah ﷺ swore most often was, "No, by the One who turns the hearts."
حدثنا عبد الله بن محمد النفيلي حدثنا ابن المبارك عن موسى بن عقبة عن سالم
أكثر ما كان رسول الله ﷺ يحلف بهذه اليمين لا ومقلب القلوب
Bukhari transmitted it in Qadr, chapter, "One who comes between a man and his heart," hadith no. 6617, from the hadith of Ibn Mubarak, through this same chain.