Musnad Ahmad 30:2811

'Abd al-Rahman narrated to us, he said: Sufyan narrated to us, from Sumayy, from Abu Salih, from Abu Hurayrah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "The accepted Hajj has no reward other than Paradise. And the two 'Umrahs expiate the sins committed between them."