It is narrated from Hazrat Abu Darda (may Allah be pleased with him) that once we were sitting with the Prophet (peace and blessings be upon him) discussing the events to come, when the Prophet (peace and blessings be upon him) said: If you hear that a mountain has moved from its place, you may believe it, but if you hear that a man's character has changed, do not believe it, because he will return to his nature.