Musnad Ahmad 512:9

Muhammad ibn Ja'far narrated to us, Shu'bah narrated to us, from 'Abd al-Malik ibn Maysarah, from Tawus, from Suraqah ibn Malik ibn Ju'sham, that he said: "O Messenger of Allah, have you considered this 'Umrah of ours, is it for this year of ours or forever?" The Messenger of Allah, peace and blessings of Allah be upon him, said: "Rather, it is forever."