Musnad Ahmad 903:1

'Abd al-Razzaq narrated to us, Ma'mar informed us, from 'Asim ibn Sulayman, from 'Abd Allah ibn Sarjis, who said: "You see this old man"—meaning himself—"I spoke to the Prophet of Allah, may Allah bless him and grant him peace, and I ate with him, and I saw the mark that was between his shoulders. It was on the edge of his left shoulder blade, as if it were a *jam'*—meaning a clenched fist—and he gestured with his hand, clenching it, [it was] moles like the appearance of warts."