It is narrated from Hazrat Abu Hurairah (may Allah be pleased with him) that once, in the presence of the Noble Prophet (peace and blessings be upon him), mention was made of a deceased man. People began to speak of his good qualities and praised him. The Noble Prophet (peace and blessings be upon him) said, "It has become obligatory." Meanwhile, mention was made of another man, and people spoke of his bad qualities and criticized him. The Noble Prophet (peace and blessings be upon him) said, "It has become obligatory." Then he said, "You are Allah's witnesses on earth."