وإذا تتلى عليهم آياتنا بينات
And when Our clear Ayat are recited to them,
means, when the Ayat of the Qur'an and clear evidence and proof for Tawhid of Allah are mentioned to them, and they are told that there is no god besides Allah and that the Messengers spoke the truth,
تعرف في وجوه الذين كفروا المنكر
you will notice a denial on the faces of the disbelievers!
يكادون يسطون بالذين يتلون عليهم آياتنا
They are nearly ready to attack with violence those who recite Our Ayat to them.
then they nearly attack and do harm to those who bring proof to them from the Qur'an, and cause them harm using their tongues and hands.
قل
Say, (O Muhammad to these people),
أفٲنبيكم بشر من ذلكم النار وعدها الله الذين كفروا
Shall I tell you of something worse than that! The Fire! which Allah has promised to those who disbelieved,
The fire and wrath and torment of Allah are far worse than that with which you are trying to scare the believing close friends of Allah in this world. The punishment in the Hereafter for these deeds of yours is worse than that what you claim you want to do to the believers.
وبيس المصير
and worst indeed is that destination!
how terrible is the Fire as a final destination and abode!
إنها ساءت مستقرا ومقاما
Evil indeed it is as an abode and as a place to rest in. (25:66)