Musnad Ahmad 27:1541

'Uthman ibn 'Umar narrated to us, Malik informed me, from Qatan ibn Wahb ibn 'Uwaymir, from Yuhannis, from Ibn 'Umar, that the Messenger of Allah (peace and blessings of Allah be upon him) said: "No one bears its hardship and its severity, except that I will be a witness for him or an intercessor on the Day of Resurrection."