"And We did not send any messenger except in the language of his people." Qatada said: Meaning, in the tongue of his people. "So that he may make it clear to them; then Allah leads astray whom He wills and guides whom He wills" after the clarification.
﴿وَمَا أَرْسَلْنَا مِنْ رَسُولٍ إِلا بِلِسَان قومه﴾ قَالَ قَتَادَة: يَعْنِي: بلغَة قَوْمِهِ ﴿لِيُبَيِّنَ لَهُمْ فَيُضِلُّ اللَّهُ مَنْ يَشَاءُ وَيَهْدِي مَنْ يَشَاءُ﴾ بعد الْبَيَان.