Tafseer of Explained in detail · Fussilat · 41:20
Until, when they reach it, their hearing and their eyes and their skins will testify against them of what they used to do.
Important: The Arabic source text is always authoritative. This translation is a study aid and has not been verified by scholars — do not use it as a basis for religious proof or for deriving rulings (ahkam). When in doubt, always consult the Arabic text and a qualified scholar.
And His word: حَتَّى إِذَا مَا جَاءُوهَا شَهِدَ عَلَيْهِمْ سَمْعُهُمْ وَأَبْصَارُهُمْ (Until, when they come to it, their hearing and their eyes testify against them) says: until, when they come to the Fire, their hearing testifies against them concerning that to which they attentively listened in the worldly life and to which they gave ear, and their eyes concerning that at which they looked in the worldly life, وَجُلُودُهُمْ بِمَا كَانُوا يَعْمَلُونَ (and their skins concerning what they used to do).
And it has been said: by "the skins" in this place the private parts are intended.
* Mention of who said that:
Ibn Ḥumayd related to us, saying: Yaʿqūb al-Qummī related to us, on the authority of al-Ḥakam al-Thaqafī, from a man of the family of Abū ʿAqīl, who traced the report back (to the Prophet): وَقَالُوا لِجُلُودِهِمْ لِمَ شَهِدْتُمْ عَلَيْنَا (And they say to their skins: why did you testify against us?) — by that only their private parts are intended, but it is referred to euphemistically.
Yūnus related to me, saying: Ibn Wahb informed us, saying: Ḥarmala related to us, that he heard ʿUbayd Allāh ibn Abī Jaʿfar say: حَتَّى إِذَا مَا جَاءُوهَا شَهِدَ عَلَيْهِمْ سَمْعُهُمْ وَأَبْصَارُهُمْ وَجُلُودُهُمْ , he said: their skins are the private parts.
And this statement which we have mentioned from the one from whom we have mentioned it, concerning the meaning of "the skins" — even though it is a meaning that the interpretation can bear — is not the most likely meaning of "the skins," nor the most well-known. And it is not permissible to transfer the well-known meaning of something onto that which it more closely resembles rather than onto another, except on the basis of a proof to which one must submit.