وَكَذَلِكَ أَنزَلْنَاهُ حُكْمًا عَرَبِيًّاAnd thus have We sent it (the Qur'an) down to be a judgement of authority in Arabic.Allah says, `Just as We sent Messengers before you and revealed to them Divine Books from heaven, We sent down to you the Qur'an, a judgement of authority in Arabic, as an honor for you, and We preferred you among all people with this clear, plain and unequivocal Book that,لااَّ يَأْتِيهِ الْبَـطِلُ مِن بَيْنِ يَدَيْهِ وَلَا مِنْ خَلْفِهِ تَنزِيلٌ مِّنْ حَكِيمٍ حَمِيدٍFalsehood cannot come to it from before it or behind it:(it is) sent down by the All-Wise, Worthy of all praise.' (41:42)Allah's statement,وَلَيِنِ اتَّبَعْتَ أَهْوَاءهُمWere you to follow their (vain) desires,means, their opinions,بَعْدَ مَا جَاءكَ مِنَ الْعِلْمِafter the knowledge which has come to you,from Allah, all praise to Him,مَا لَكَ مِنَ اللّهِ مِن وَلِيٍّ وَلَا وَاقٍthen you will not have any Wali (protector) or defender against Allah.This part of the Ayah warns people of knowledge against following the paths of misguidance after they had gained knowledge in (and abided by) the Prophetic Sunnah and the path of Muhammad, may Allah's best peace and blessings be on him