The rain was falling on the day when the Battle of Hunayn took place. The Prophet ﷺ, therefore, commanded that the people should offer their prayer in their camps.  

أَنَّ يَوْمَ حُنَيْنٍ كَانَ يَوْمَ مَطَرٍ فَأَمَرَ النَّبِيُّ ﷺ مُنَادِيَهُ أَنِ الصَّلاَةُ فِي الرِّحَالِ  

That took place on a Friday.  

أَنَّ ذَلِكَ كَانَ يَوْمَ جُمُعَةٍ  

Usamah attended the Prophet ﷺ on the occasion of the treaty of al-Hudaybiyyah on Friday. The rain fell as little as the soles of the shoes of the people were not set. He (the Prophet) commanded them to offer Friday prayer in their dwellings.  

أَنَّهُ شَهِدَ النَّبِيَّ ﷺ زَمَنَ الْحُدَيْبِيَةِ فِي يَوْمِ جُمُعَةٍ وَأَصَابَهُمْ مَطَرٌ لَمْ تَبْتَلَّ أَسْفَلُ نِعَالِهِمْ فَأَمَرَهُمْ أَنْ يُصَلُّوا فِي رِحَالِهِمْ