Musnad Ahmad 1156:114

Ubaydah narrated to us, he said: Yazid ibn Abi Ziyad narrated to me, from Abdullah ibn al-Harith, he said: I asked him about the two rak'ahs after the Asr prayer? He said: I and Abdullah ibn Abbas entered upon Mu'awiyah. Mu'awiyah said: O Ibn Abbas, you have mentioned two rak'ahs after the Asr prayer, and it has reached me that people pray them, yet we did not see the Messenger of Allah, peace and blessings of Allah be upon him, pray them, nor did he command them. Ibn Abbas said: That is what Ibn al-Zubayr gives fatwa to the people about. He said: Then Ibn al-Zubayr came. He said: What are the two rak'ahs you give fatwa to the people about? Ibn al-Zubayr said: Aisha narrated to me from the Messenger of Allah, peace and blessings of Allah be upon him. He said: So he sent two men to Aisha, saying: The Commander of the Faithful sends you greetings of peace, and says: What are the two rak'ahs that Ibn al-Zubayr claims you commanded him to perform after the Asr prayer? She said: That is what Umm Salamah informed him of. He said: So we entered upon Umm Salamah and informed her of what Aisha said. She said: May Allah have mercy on her, did I not inform her that the Messenger of Allah, peace and blessings of Allah be upon him, had forbidden them?