The Holy Quran 6:8 — Surah Al-An'am
Arabic text
وَقَالُوا۟ لَوْلَآ أُنزِلَ عَلَيْهِ مَلَكٌ ۖ وَلَوْ أَنزَلْنَا مَلَكًا لَّقُضِىَ ٱلْأَمْرُ ثُمَّ لَا يُنظَرُونَ
Translation
They (the Kuffaar also) say, "Why is an angel not sent to him (to Muhammad ﷺ to verify that he is a prophet)?" If We were to send an angel (as they request and if they still refuse to accept that he is a Prophet), the matter (of their punishment) will be decided and then they (will be destroyed immediately and they) will not be granted respite (to repent).
Tafsir (excerpt) — Tafsir Usmani
The demand that an angel be sent: that is, [an angel] who would appear before us and bear witness to his truthfulness. The wisdom in not fulfilling the demands of the idolaters: if an angel were to come in his true form, these people could not bear it even for a minute; they would breathe their last from his awe and majesty.
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