وَهُمْ يَنْهَوْنَ عَنْهُ وَيَنْأَوْنَ عَنْهُ
...
And they prevent others from him and they themselves keep away from him,
They discourage people from following the truth, believing in Muhammad and obeying the Qur'an,
وَيَنْأَوْنَ عَنْهُ
(and they themselves keep away from him),
They thus combine both evil acts, for they neither benefit themselves, nor let others benefit from the Prophet.
Ali bin Abi Talhah said that Ibn Abbas said that the Ayah,
وَهُمْ يَنْهَوْنَ عَنْهُ
(And they prevent others from him), means,
they hinder people from believing in Muhammad.
Muhammad bin Al-Hanafiyyah said,
"The disbelievers of Quraysh used to refrain from meeting Muhammad and they discouraged people from coming to him."
Similar was reported from Qatadah, Mujahid and Ad-Dahhak and several others.
...
وَإِن يُهْلِكُونَ إِلاَّ أَنفُسَهُمْ وَمَا يَشْعُرُونَ
and (by doing so) they destroy not but themselves, yet they perceive (it) not.
They destroy themselves by committing this evil action, and its harm will only touch them. Yet, they do not perceive this fact!