It is reported about Sayyidah Umm Salamah (may Allah be pleased with her) that she swore an oath concerning a slave of hers who had asked her to free him. Sayyidah Umm Salamah (may Allah be pleased with her) swore: "If I ever free him, may Allah Almighty not free me from Hell." Then as much time passed as Allah willed, and Sayyidah Umm Salamah (may Allah be pleased with her) said: "Subhan Allah! I heard the Prophet (peace and blessings be upon him) say: 'Whoever swears an oath and then sees something better than it, let him give expiation for his oath and do what is better.'" Then Sayyidah Umm Salamah (may Allah be pleased with her) freed the slave and gave expiation for her oath.
Imam al-Tabarani recorded it in al-Mu'jam al-Kabir, and its narrators are thiqat (trustworthy), except that Abdullah bin Hasan did not hear from Sayyidah Umm Salamah (may Allah be pleased with her).