Sayyidah Umm Salamah (may Allah be pleased with her) narrates that the Prophet (peace and blessings be upon him) said: "Whoever prays four rak'ahs before Asr, Allah Almighty makes his body forbidden to Hellfire." I said: "O Messenger of Allah! I have seen you sometimes pray these rak'ahs and sometimes leave them." The Prophet (peace and blessings be upon him) said: "I am not like any one of you."
Al-Tabarani recorded it in al-Mu'jam al-Kabir; its chain contains Nafi' bin Mihran, and there are other narrators besides him whom I did not find anyone mentioning.