"And to Madyan" means: We sent to the people of Madyan, "their brother Shu'ayb," their brother by lineage, not their brother in religion.
"Indeed, I see you in prosperity" means: in prosperity from Allah; that is, in abundance and sustenance. They were people who gave short measure in weights and diminished the scales.
﴿وَإِلَى مَدين﴾ أَيْ: وَأَرْسَلْنَا إِلَى أَهْلِ مَدْيَنَ ﴿أَخَاهُم شعيبا﴾ أَخُوهُمْ فِي النَّسَبِ، وَلَيْسَ بِأَخِيهِمْ فِي الدِّينِ.
﴿إِنِّي أَرَاكُمْ بِخَيْرٍ﴾ أَيْ: بِخَيْرٍ مِنَ اللَّهِ؛ يَعْنِي: السَّعَةَ وَالرِّزْقَ، وَكَانُوا أَصْحَابَ تَطْفِيفٍ فِي الْكَيْلِ، وَنُقْصَانٍ مِنَ الْمِيزَانِ.
