Sahih al-Bukhari 4123
Narrated Al-Bara:
The Prophet (ﷺ) 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 Messenger (ﷺ) said to Hassan bin Thabit, 'Abuse them (with your poems), and Gabriel is 
with you (i.e. supports you).' "
حَدَّثَنَا الْحَجَّاجُ بْنُ مِنْهَالٍ، أَخْبَرَنَا شُعْبَةُ، قَالَ أَخْبَرَنِي عَدِيٌّ، أَنَّهُ سَمِعَ الْبَرَاءَ ـ رضى الله عنه ـ قَالَ قَالَ النَّبِيُّ صلى الله عليه وسلم لِحَسَّانَ ‏
"‏ اهْجُهُمْ ـ أَوْ هَاجِهِمْ ـ وَجِبْرِيلُ مَعَكَ ‏"‏‏.‏