Speech as Indicator of Faith

وَلَوْ نَشَآءُ لَأَرَيْنَـٰكَهُمْ فَلَعَرَفْتَهُم بِسِيمَـٰهُمْ ۚ وَلَتَعْرِفَنَّهُمْ فِى لَحْنِ ٱلْقَوْلِ ۚ وَٱللَّهُ يَعْلَمُ أَعْمَـٰلَكُمْ

And if We willed, We could show them to you, and you would know them by their mark; but you will surely know them by the tone of [their] speech. And Allāh knows your deeds.