﴿ بَلْ كَذَّبُوا۟ بِٱلْحَقِّ لَمَّا جَآءَهُمْ فَهُمْ فِىٓ أَمْرٍۢ مَّرِيجٍ ﴾

“Nay, but they [who refuse to believe in resurrection] have been wont to give the lie to this truth whenever it was proffered to them; and so they are in a state of confusion.”

(Nay, but they) the Quraysh (have denied the Truth) Muhammad (pbuh) and the Qur'an (when it came unto them) this is the second clause of the oath, i.e. by the noble and glorious Qur'an, Muhammad (pbuh) has brought them the Qur'an, (therefore they are now in troubled case) they are in error; it is also said that this means: they are confused; and it is also said this means: they are in disagreement, some of them believe while others do not.