ٱلَّذِينَ تَتَوَفَّىٰهُمُ ٱلْمَلَٰٓئِكَةُ ظَالِمِىٓ أَنفُسِهِمْ فَأَلْقَوُا۟ ٱلسَّلَمَ مَا كُنَّا نَعْمَلُ مِن سُوٓءٍۭ بَلَىٰٓ إِنَّ ٱللَّهَ عَلِيمٌۢ بِمَا كُنتُمْ تَعْمَلُونَ · فَٱدْخُلُوٓا۟ أَبْوَٰبَ جَهَنَّمَ خَٰلِدِينَ فِيهَا فَلَبِئْسَ مَثْوَى ٱلْمُتَكَبِّرِينَ
Alladhīna tatawaffāhumu'l-malāʾikatu ẓālimī anfusihim, fa-alqawu'l-salama mā kunnā naʿmalu min sūʾ, balā inna'llāha ʿalīmun bimā kuntum taʿmalūn · Fa'dkhulū abwāba jahannama khālidīna fīhā, fa-la-biʾsa mathwa'l-mutakabbirīn
"Those whom the angels take while they are wronging themselves surrender: 'We were doing no evil.' No indeed! God knows what you were doing. · So enter the gates of Hell, to remain in them. Evil is the abode of those who make themselves great!"
To cast down the salam — to lay surrender out in the open, to give oneself up. Root س-ل-م: to be sound, to be without flaw, to surrender.
And the choice of verb is worth recording: alqaw — "they cast, they threw down". The same verb was used of the mountains in the fifteenth verse (wa alqā fi'l-arḍi rawāsiya). This is a repetition verifiable within the sūra; but the agent changes between the two uses: there it is God who casts, here it is man who throws down.
مَا كُنَّا نَعْمَلُ مِن سُوٓءٍ — and even after the surrender a defence follows. The order of the sentence must be recorded: first the surrender, then the denial. The two movements do not normally stand together.
I give this as an observation: the verse shows that surrender is not acceptance — even when the resistance is over, the defence continues.
And the answer is a single word: balā — "no, it is not so". In Arabic balā is a particle used specifically to refute a negative sentence; naʿam (yes) would have confirmed the negation. The claim is refuted in one syllable.
مَثْوَى — root ث-و-ي: to stay in a place, to lodge. Mathwā — the place where one stays. The word occurred at Muḥammad, 47/12 (wa'l-nāru mathwan lahum).