Mukhtasar Muslim

Narrated from Abu Huraira (may Allah be pleased with him) that the Messenger of Allah (peace and blessings of Allah be upon him) said: A servant utters a word without realizing its gravity, and because of it he sinks into the Fire as far as the distance between the east and the west (such as complaining about a Muslim or informing against him to the rulers, or slander, or abuse, or a word of disbelief, or mocking the Messenger of Allah (peace and blessings of Allah be upon him), or the Qur'an, or the Shari'ah. Therefore, a person should control his tongue and not speak without necessity).