Overall meaning : Allah, Glorified and Exalted be He, condemns those who deny His signs and revelations and, worse still, persist in their tyranny and grow even more stubborn in clinging to error so much as they kill Allah’s prophets and messengers unjustly and kill those among Allah’s servants who call to justice  and enjoin good and forbid evil. He instructs His Messenger to inform them that a painful torment awaits them because of their unbelief and evil deeds.
He further states that these people’s works will bear no fruit and will not benefit them at all neither in this world nor in the world to come, nor will they find anyone to help them or protect them against Allah’s punishment when He inflicts it on them.