Humran (may Allah have mercy on him) said: Sayyiduna Mu'awiyah bin Abi Sufyan (may Allah be pleased with him) addressed us in a sermon and said: "You pray a prayer that the Messenger of Allah (peace and blessings be upon him) did not pray; rather, he (peace and blessings be upon him) used to forbid it," meaning the two rak'ahs after Asr.
Hadith Referenceالمعجم الكبير للطبراني / باب الميم / 16815