"And thus have We revealed it as an Arabic judgment," meaning: the Quran.

"And if you were to follow their desires," meaning: the polytheists, so that you would not convey the Message from Allah.

"You would have no protector or defender against Allah," that would save you from His punishment; if you were to do so, though you would not do so.

Surat Ar-Ra'd from verse (38) to verse (43).