﴿ وَلَئِن سَأَلْتَهُمْ لَيَقُولُنَّ إِنَّمَا كُنَّا نَخُوضُ وَنَلْعَبُ ۚ قُلْ أَبِٱللَّهِ وَءَايَٰتِهِۦ وَرَسُولِهِۦ كُنتُمْ تَسْتَهْزِءُونَ ﴾

“Yet, indeed, if thou wert to question them. they would surely answer, "We were only indulging in idle talk, and were playing [with words]. Say: "Were you, then. mocking at God and His messages and His Apostle?”

And if la-in the lām is for oaths you question them about their mockery of you and of the Qur’ān while they were journeying with you towards Tabūk assuredly they will say making excuses ‘We were only engaging in idle talk and jesting’ in conversation in order to pass the time of the road and we did not mean it. Say to them ‘Were you then mocking God and His signs and His Messenger?