فَٱصْدَعْ بِمَا تُؤْمَرُ وَأَعْرِضْ عَنِ ٱلْمُشْرِكِينَ
Fasda' bimaa tu'maru wa a'rid anil mushrikeen
So proclaim openly what you have been commanded [to say], and ignore the idolaters.
So proclaim openly what you are commanded, and turn away from those who associate others with God.
Sada'a describes splitting something that was whole: the earth cracking open for what grows at 86:12, a gathering breaking apart at 30:43, the splitting headache denied to the garden's wine at 56:19. Choosing that verb for the command to proclaim treats public speech as an act that divides a community which had held together, and the protection promised straight afterwards is against mockers. Early readers differed over whether it means speak out or separate truth from falsehood.