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 Apostle ﷺ said to Hassan bin Thabit, 'Abuse them (with your poems), and Gabriel is with you (i.e. supports you).' "

وَزَادَ إِبْرَاهِيمُ بْنُ طَهْمَانَ عَنِ الشَّيْبَانِيِّ، عَنْ عَدِيِّ بْنِ ثَابِتٍ، عَنِ الْبَرَاءِ بْنِ عَازِبٍ، قَالَ رَسُولُ اللَّهِ ﷺ يَوْمَ قُرَيْظَةَ لِحَسَّانَ بْنِ ثَابِتٍ " اهْجُ الْمُشْرِكِينَ، فَإِنَّ جِبْرِيلَ مَعَكَ ".