صحيح مسلم

Ibn Abu Mulaika reported: I heard `A'isha as saying and she was asked as to whom Allah's Messenger (ﷺ) would have nominated as his successor if he had to nominate one at all. She said: Abu Bakr. It was said to her: Then whom after Abu Bakr? She said: `Umar. It was said to her. Then whom after `Umar? She said: Abu `Ubaida b. al-Jarrah, and then she kept quiet at this.