Surat Saba' - سورة سبأ

وَمَا كَانَ لَهُ عَلَيْهِم مِّن سُلْطَانٍ إِلَّا لِنَعْلَمَ مَن يُؤْمِنُ بِالْآخِرَةِ مِمَّنْ هُوَ مِنْهَا فِي شَكٍّ ۗ وَرَبُّكَ عَلَىٰ كُلِّ شَيْءٍ حَفِيظٌ

Muhsin Khan: And he (Iblis Satan) had no authority over them, except that We might test him, who believes in the Hereafter from him who is in doubt about it. And your Lord is a Hafiz over everything. (AllKnower of everything i.e. He keeps record of each and every person as regards deeds, and then He will reward them accordingly).