التفسير: يوسف ٣:١٢

In the third verse, it was said: نَحْنُ نَقُصُّ عَلَيْكَ أَحْسَنَ الْقَصَصِ بِمَا أَوْحَيْنَا إِلَيْكَ هَـٰذَا الْقُرْ‌آنَ وَإِن كُنتَ مِن قَبْلِهِ لَمِنَ الْغَافِلِین (We narrate to you the best narrative by revealing this Qur'an to you, and surely before this, you were among the unaware).

This is to chasten the Jews that they had tried to test the Messenger of Allah ﷺ which proved to be in vain, for its effect turned out to be just the reverse of what they had intended. It only went on to prove the excellence and authenticity of the Messenger of Allah ﷺ in a far more evident manner. From this it became clear that he was already an Ummiyy and had no knowledge of world history. Now that he came to know of this needs an explanation and there can be no explanation for this except that he was Divinely educated and blessed with revelation as a prophet of Allah Ta’ ala.