Sayyiduna Anas (may Allah be pleased with him) said: A funeral passed by the Prophet (peace and blessings be upon him) and the deceased was praised, so he (peace and blessings be upon him) said: "It has become due." Another funeral passed and the deceased was spoken of badly, so he (peace and blessings be upon him) said: "It has become due." It was said to him (peace and blessings be upon him): What has become due for both? He (peace and blessings be upon him) said: "The believers are Allah's witnesses on the earth."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب آداب القاضي / 20389
Abu Bakr bin Abi Zuhayr al-Thaqafi narrates from his father (may Allah be pleased with him): I heard the Prophet (peace and blessings be upon him) at al-Nabah, or al-Nabawah, saying: "Soon you will distinguish the people of Paradise from the people of Hell," or he said: "your best from your worst." It was said: O Messenger of Allah! How so? He said: "By good and bad praise; some of you are witnesses over others."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب آداب القاضي / 20390