Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) said that the Messenger of Allah (peace and blessings be upon him) said: "Whoever's intercession stands in the way of one of the hadd punishments of Allah has defied Allah in His sovereignty. Whoever dies in debt, there will be no dinar or dirham there, but only good deeds and bad deeds. Whoever knowingly disputes in support of falsehood remains under the displeasure of Allah until he desists. And whoever says about a believer something that is not in him will be confined in Radghat al-Khabal ('the reservoir of the pus and blood of the people of Hell') until he comes out of what he said."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الوكالة / 11441
It is narrated from Sayyiduna Abu Hurayrah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Whoever walks with a people making it appear that he is a witness when he is not a witness is a false witness; whoever helps in a dispute without knowledge remains under the displeasure of Allah until he desists; and killing a Muslim is disbelief, and abusing him is sinfulness."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الوكالة / 11444