Military Expeditions led by the Prophet (pbuh) (Al-Maghaazi)

Bukhari :: Book 5 :: Volume 59 :: Hadith 449

Narrated Al-Bara:

The Prophet said to Hassan, "Abuse them (with your poems), and Gabriel is with you (i.e, supports you)." (Through another group of sub narrators) Al-Bara bin Azib said, "On the day of Quraiza's (besiege), Allah's Apostle said to Hassan bin Thabit, 'Abuse them (with your poems), and Gabriel is with you (i.e. supports you).' "