"And you were not concealing yourselves," meaning: you were not hiding; according to the tafsir of Mujahid, "that your hearing, your sights, or your skins would testify against you. But you thought," you assumed, "that Allah does not know much of what you do."
﴿وَمَا كُنْتُم تستترون﴾ أَي: تَتَّقُون؛ فِي تَفْسِير مُجَاهِد ﴿أَنْ يَشْهَدَ عَلَيْكُمْ سَمْعُكُمْ وَلا أَبْصَارُكُمْ وَلا جُلُودُكُمْ وَلَكِنْ ظَنَنْتُمْ﴾ حسبتم ﴿أَنَّ اللَّهَ لَا يَعْلَمُ كثيرا مِمَّا تَعْمَلُونَ﴾
