It is narrated from Ibn Abbas, may Allah be pleased with him, that two men performed the Zuhr or Asr prayer while they were fasting. When the Prophet, peace and blessings be upon him, had finished the prayer, he said: "Both of you should repeat your ablution, repeat the prayer, complete your fast, and make up for it on another day." Both of them asked: O Messenger of Allah! Why? He, peace and blessings be upon him, said: "You have backbitten such-and-such person." Its chain is weak. Narrated by Al-Bayhaqi in Shu'ab al-Iman.