﴿ نَحْنُ نَقُصُّ عَلَيْكَ أَحْسَنَ ٱلْقَصَصِ بِمَآ أَوْحَيْنَآ إِلَيْكَ هَٰذَا ٱلْقُرْءَانَ وَإِن كُنتَ مِن قَبْلِهِۦ لَمِنَ ٱلْغَٰفِلِينَ ﴾

“In the measure that We reveal this Qur'an unto thee, [O Prophet,] We explain it to thee in the best possible way, seeing that ere this thou wert indeed among those who are unaware [of what revelation is].”

We will relate to you the best of narratives in what We have revealed in Our revealing to you this Qur’ān though wa-in in is softened in other words understand it as wa-innahu prior to it you were of the heedless.