Musannaf Ibn Abi Shayba 27:19

Hatim ibn Isma'il narrated to us, from al-Muhajir ibn al-Mismar, from 'Amir ibn Sa'd, who said: I wrote to Jabir ibn Samurah, "Inform me of something you heard from the Messenger of Allah, may Allah bless him and grant him peace." He said: So he wrote, "Indeed, I heard him saying, 'I am the forerunner at the Basin (al-Hawd).'"