'A'isha reported that Abu Bakr cursed one of his slaves and the
Prophet, may Allah bless him and grant him peace, said, "Abu Bakr! The
cursers and the true! No, by the Lord of the Ka'ba," and he repeated that
two or three times. That very same day Abu Bakr freed one of his slaves.
The Prophet, may Allah bless him and grant him peace, came and said, "Do
not do that again (i.e. curse someone)."