Musnad Ahmad 512:10

Husayn ibn Muhammad narrated to us, Shu'bah narrated to us, from 'Abd al-Malik, who said: I heard Tawus narrating from Suraqah ibn Malik al-Kinani—and he did not hear it from him, thus it is in the hadith—that he asked the Prophet, peace and blessings of Allah be upon him, and said: "O Messenger of Allah, is this 'Umrah of ours for this year of ours, or is it forever?" He said: "Forever."