Sahih Bukhari Volume 4, Book 55, Hadith Number 555.

Narated By Abu Said : Allah’s Apostle said, “Noah and his nation will come (on the Day of Resurrection and Allah will ask (Noah), “Did you convey (the Message)?’ He will reply, ‘Yes, O my Lord!’ Then Allah will ask Noah’s nation, ‘Did Noah convey My Message to you?’ They will reply, ‘No, no prophet came to us.’ Then Allah will ask Noah, ‘Who will stand a witness for you?’ He will reply, ‘Muhammad and his followers (will stand witness for me).’ So, I and my followers will stand as witnesses for him (that he conveyed Allah’s Message).” That is, (the interpretation) of the Statement of Allah: “Thus we have made you a just and the best nation that you might be witnesses Over mankind…” (2.143)