وَلَئِن سَأَلْتَهُمْ لَيَقُولُنَّ إِنَّمَا كُنَّا نَخُوضُ وَنَلْعَبُ ۚ قُلْ أَبِاللَّهِ وَآيَاتِهِ وَرَسُولِهِ كُنتُمْ تَسْتَهْزِئُونَ
“If you question them, they will certainly say, "We were only talking idly and joking around." Say, "Was it Allah, His revelations, and His Messenger that you ridiculed?"”
The hypocrites' idle-talk/joking excuse, same incident as the adjacent verses 9:64 and 9:66 already linked to this event.