﴿ إِنَّهُمْ يَكِيدُونَ كَيْدًۭا ﴾

“Behold, they [who refuse to accept it] devise many a false argument [to disprove its truth];”

(Lo! They) i.e. the people of Mecca (plot a plot (against thee, O Muhammad)) they scheme in their state of disbelief, that is to say they bar people from Muhammad (pbuh) and from the Qur'an; it is also said this means: they plan, in Dar al-Nadwah, to kill you, O Muhammad!