مَا كُنتَ تَعْلَمُهَآ أَنتَ وَلاَ قَوْمُكَ مِن قَبْلِ هَـذَا
(neither you nor your people knew it before this.) This means that neither you (Muhammad ) nor anyone of your people, have any knowledge of this. This is so that no one who rejects you can say that you learned it from him. Rather, it was Allah Who informed you of it in conformity with the true situation (of the story), just as the Books of the Prophets who were before you testify to. Therefore, you should be patient with the rejection of your people and their harming you. For verily, We shall help you and surround you with Our aid. Then, We will make the (good) end for you and those who follow you in this life and the Hereafter. This is what We did with the Messengers when We helped them against their enemies.