Surah At-Tawba 9:65

If you ask them (about this), they declare: "We were only talking idly and joking." Say: "Was it at Allah, and His Ayat and His Messenger that you were mocking (65)Make no excuse; you disbelieved after you had believed. If We pardon some of you, We will punish others among you because they were criminals (66)

The Hypocrites rely on False, Misguided Excuses

Abdullah bin 'Umar said, "During the battle of Tabuk, a man was sitting in a gathering and said, 'I have never seen like these reciters of ours! They have the hungriest stomachs, the most lying tongues and are the most cowardice in battle.' A man in the Masjid said, 'You lie. You are a hypocrite, and I will surely inform the Messenger of Allah ﷺ.' This statement was conveyed to the Messenger of Allah ﷺ and also a part of the Qur'an was revealed about it.'" 'Abdullah bin 'Umar said, "I have seen that man afterwards holding onto the shoulders of the Messenger's camel while stones were falling on him, declaring, 'O Allah's Messenger! We were only engaged in idle talk and jesting,' while the Messenger of Allah ﷺ was reciting,

أَبِاللَّهِ وَآيَاتِهِ وَرَسُولِهِ كُنتُمْ تَسْتَهْزِئُونَ

("Was it at Allah, and His Ayat and His Messenger that you were mocking?")[9:65].'" Allah said,

لَا تَعْتَذِرُوا قَدْ كَفَرْتُم بَعْدَ إِيمَانِكُمْ

(Make no excuse; you disbelieved after you had believed.) on account of your statement and mocking,

إِن نَّعْفُ عَن طَائِفَةٍ مِّنكُمْ نُعَذِّبْ طَائِفَةً

(If We pardon some of you, We will punish others among you) for not all of you will be forgiven, some will have to taste the torment,

بِأَنَّهُمْ كَانُوا مُجْرِمِينَ

(because they were criminals), they were criminals because of this terrible, sinful statement.