Musnad Abu Ya'la al-Mawsili 209:49

Harun narrated to us, Ibn Abi Fudayk narrated to us, Abdullah bin Abd al-Rahman bin Yahnas narrated to us, he said: Yahya bin Abi Sufyan bin Sa'id al-Akhnasi narrated to me, from his grandmother Hakimah, from Umm Salamah, that she heard the Messenger of Allah (peace be upon him) saying: "Whoever enters into the state of Ihram for Hajj or Umrah from al-Masjid al-Aqsa to al-Masjid al-Haram, his past and future sins will be forgiven," or "Paradise will be mandatory for him." Abdullah was in doubt as to which of the two he said.