Surah Hud Tafseer

فَإِلَّمْ يَسْتَجِيبُواْ لَكُمْ

If then they answer you not,

Meaning, that if they do not come with a reply to that which you have challenged them with (to the reproduction of ten chapters like the Qur'an), then know that it is due to their inability to do so.

فَاعْلَمُواْ أَنَّمَا أُنزِلِ بِعِلْمِ اللّهِ

know then that it is sent down with the knowledge of Allah,

Know (that this is a proof) that this is the speech revealed from Allah. It contains His knowledge, His commands and His prohibitions.

Then Allah continues by saying,

وَأَن لاَّ إِلَـهَ إِلاَّ هُوَ فَهَلْ أَنتُم مُّسْلِمُونَ

and that there is no God besides Him! Will you then be Muslims