لَا تَعْتَذِرُوا قَدْ كَفَرْتُم بَعْدَ إِيمَانِكُمْ ۚ إِن نَّعْفُ عَن طَائِفَةٍ مِّنكُمْ نُعَذِّبْ طَائِفَةً بِأَنَّهُمْ كَانُوا مُجْرِمِينَ
“Make no excuses. You have committed kufr after your Iman.”
This ayah is part of Surat al-Tawba's Tabuk-era passage addressing the hypocrites and excuse-makers who stayed behind or mocked the campaign, described at this event.
This is the specific asbab al-nuzul the post narrates: the ayah exposing the hypocrites' "joking" excuse was revealed as the accused ran up to make it.