Musnad Ahmad 27:439

'Abd al-Razzaq narrated to us, Ma'mar informed us, from al-Zuhri, from Salim, from Ibn 'Umar, who said: "I have not ceased touching the two corners (the Black Stone and the Yemeni Corner) in times of ease or hardship since I saw the Messenger of Allah, peace and blessings of Allah be upon him, touching them."