Abdullah bin al-Hasan (may Allah have mercy on him) narrates from Sayyidah Umm Salamah (may Allah be pleased with her) that, concerning a slave of hers who had asked her for his freedom, she swore an oath and said: May Allah never free me from the Fire if I ever free him. Then she remained (so) for as long as Allah willed, and then said: Subhan Allah! I heard the Messenger of Allah (peace and blessings be upon him) say: "Whoever swears an oath about something and then sees something better than it, let him make expiation for his oath and then do that which is better." So I freed the slave, and then made expiation for my oath.
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 19998
It is narrated from Sayyidah Umm Salamah (may Allah be pleased with her) that the Messenger of Allah (peace and blessings be upon him) said: "Whoever does not have one of these three qualities, let him not count on anything: God-consciousness (taqwa) that keeps him from forbidden things, or forbearance with which he can restrain himself from the foolish person, or good character by which he can live agreeably among people."
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 19999