يَا أَيُّهَا الَّذِينَ آمَنُوا اذْكُرُوا نِعْمَةَ اللَّهِ عَلَيْكُمْ إِذْ جَاءَتْكُمْ جُنُودٌ فَأَرْسَلْنَا عَلَيْهِمْ رِيحًا وَجُنُودًا لَّمْ تَرَوْهَا ۚ وَكَانَ اللَّهُ بِمَا تَعْمَلُونَ بَصِيرًا
“O believers! Remember Allah's favor upon you when [enemy] forces came to [besiege] you [in Madinah], so We sent against them a [bitter] wind and forces you could not see. And Allah is All-Seeing of what you do.”
This ayah recalls the wind and unseen forces Allah sent against the confederate armies at the Trench -- the retreat the post reports being announced.