"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).
﴿وَكَذَلِكَ أَنزَلْنَاهُ حكما عَرَبيا﴾ يَعْنِي: الْقُرْآنَ.
﴿وَلَئِنِ اتَّبَعْتَ أَهْوَاءَهُمْ﴾ يَعْنِي: الْمُشْرِكِينَ حَتَّى لَا تُبَلِّغُ عَنِ اللَّهِ الرِّسَالَةَ.
﴿مَا لَكَ مِنَ اللَّهِ مِنْ وَلِيٍّ وَلا واق﴾ يُغْنِيكَ مِنْ عَذَابِهِ؛ إِنْ فَعَلْتَ، وَلست بفاعلٍ.
سُورَة الرَّعْد من الْآيَة (٣٨) إِلَى الْآيَة (٤٣).