Witnesses

Sayyiduna Abu Hurayrah (may Allah be pleased with him) narrates: I heard the Prophet (peace and blessings be upon him) say: "Whoever gives testimony against a Muslim for which he is not qualified, let him be ready to reach his particular abode in Hell."
Ahmad recorded it; the Tabi'i in it is not named, and the rest of its narrators are thiqat (trustworthy).

Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) reports this saying of the Prophet (peace and blessings be upon him): "Because of the terror of the Day of Resurrection, the birds strike their beaks on the ground and move their tails; and when a false witness speaks, he is thrown into Hell before his feet move from their place." (Allamah al-Haythami says:) I say: Ibn Majah recorded part of this narration.
Al-Tabarani recorded it in al-Mu'jam al-Awsat, and its chain contains a narrator whom I do not know.

Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) reports this saying of the Prophet (peace and blessings be upon him): "Whoever gives testimony by which the wealth of a Muslim man is made lawful, or by which his blood is shed, has made Hell obligatory for himself."
Al-Tabarani recorded it in al-Mu'jam al-Kabir, and al-Bazzar also recorded it, adding these words: "Whoever drinks a drink until the intellect that Allah Almighty gave him departs has committed one of the major sins."
Abu Ya'la also recorded it, except that he narrated these words: "Whoever (meaning) conceals testimony and thereby seizes the wealth of a Muslim," and the rest of the narration is as before. Its chain contains Hanash, whose name is Husayn bin Qays, and he is matruk (abandoned), while Abu Mihsan claimed that he was a truthful shaykh.

Sayyiduna Abu Musa al-Ash'ari (may Allah be pleased with him) reports this saying of the Prophet (peace and blessings be upon him): "Whoever is called to give testimony and conceals it is like one who gives false testimony."
Al-Tabarani recorded it in al-Mu'jam al-Kabir and al-Mu'jam al-Awsat; its chain contains Abdullah bin Salih, whom Abd al-Malik bin Shu'ayb bin al-Layth declared thiqah (trustworthy), saying: He is thiqah and ma'mun (reliable). A group declared him da'if (weak).

Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) says: False testimony has been made equal to associating partners with Allah Almighty. Then he recited this verse: "And shun false speech."
Al-Tabarani recorded it in al-Mu'jam al-Kabir, and its chain is hasan (good).

Sayyiduna Abu al-Darda' (may Allah be pleased with him) reports this saying of the Prophet (peace and blessings be upon him): "Any man whose intercession becomes an obstacle to one of the hudud (prescribed punishments) of Allah Almighty remains continually under the displeasure of Allah Almighty until he desists. Any man who shows anger against a Muslim in a dispute about which he has no knowledge has stubbornly opposed the right of Allah Almighty and shown eagerness for His displeasure; upon such a man is the curse of Allah Almighty, which continues until the Day of Resurrection. And any man who spreads a word against a Muslim man while that man is innocent of it, intending thereby to revile him in this world, it is binding upon Allah Almighty to melt him in the Fire of Hell on the Day of Resurrection until he brings something by which he can get out of (the punishment for) what he said."

In one narration the wording is: Sayyiduna Abu al-Darda' (may Allah be pleased with him) reports this saying of the Prophet (peace and blessings be upon him): "Whoever mentions a person with something that is not in him, intending thereby to find fault with him, Allah Almighty will confine him in the Fire of Hell until he brings something by which he makes amends for what he said about that person." Al-Tabarani recorded all these narrations in al-Mu'jam al-Kabir; the chain of the first narration contains a narrator whom I do not know, and the narrators of the second narration are thiqat (trustworthy).