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 ate the flesh of his brother in this world (that is, backbit him), it (that flesh) will be brought near to him on the Day of Resurrection and it will be said to him: 'Eat it alive as you ate it dead.' So he will eat it, his face will contort (with pain and disgust), and he will scream and cry out."
Imam al-Tabarani (may Allah have mercy on him) said: "No one besides Muhammad bin Salamah (may Allah have mercy on him) narrated this hadith from Ibn Ishaq (may Allah have mercy on him)."
Hadith Referenceالمعجم الأوسط / باب الألف / 1656
Hadith Gradingمحدثین:إسناده ضعيف، فيه ابن إسحاق مدلس ومن لا يُعرف
Hadith Takhrij«قال ابن حجر: سنده حسن «فتح الباري شرح صحيح البخاري، ج 10، ص 485»» «قال الهيثمي: فيه ابن إسحاق وهو مدلس ومن لم أعرفه «مجمع الزوائد ومنبع الفوائد، ج 8، ص 92»» «أخرجه الطبراني فى «الأوسط» برقم: 5853»