(Thus have We revealed it) thus have We sent Gabriel with the Qur'an, (a decisive utterance) the whole Qur'an is Allah's judgement (in Arabic) in the Arabic usage (and if thou shouldst follow their desires) their religion and Qiblah (after that which hath come unto thee of knowledge) after Abraham's Religion and Qiblah were made clear to you, (then truly wouldst thou have from Allah) from Allah's torment (no protecting friend) nearby to benefit you (nor defender) to save you from the torment.