عَنْ حُذَيْفَةَ بْنِ الْيَمَانِ رَضِيَ اللَّهُ عَنْهُ أَنَّهُ قَالَ لِسَعِيدِ بْنِ الْعَاصِ رَضِيَ اللَّهُ عَنْهُ: وَتَأْمُرُ أَصْحَابَكَ إِنَّ هَاجَهُمْ هَيْجٌ مِنَ الْعَدُوِّ، فَقَدْ حَلَّ لَهُمْ الْقِتَالُ وَالْكَلَامُ
It is narrated from Sayyiduna Hudhayfah bin Yaman (may Allah be pleased with him) that he said to Sayyiduna Sa'id bin 'As (may Allah be pleased with him): Tell your companions that if (during prayer) the enemy attacks, then both fighting and speaking are permissible for them.