From Sahih Muslim (Hadith 4601):
This tradition has been narrated by Hishim through the same chain of transmitters with a little difference in the wording. He said:(His wound) began to bleed that very night and it continued to bleed until he died. He has made the addition that it was then that (a non-believing) poet said: Hark, O Sa'd, Sa'd of Banu Mu'adh, What have the Quraiaa and Nadir done? By thy life! Sa'd b. Mu'adh>br> Was steadfast on the morn they departed. You have left your cooking-pot empty, While the cooking-pot of the people is hot and boiling. Abu Hubab the nobleman has said, O Qainuqa', do not depart. They were weighty in their country just aa rocks are weighty in Maitan
Reference: Muslim 4601