Surah Ali 'Imran 3:144

وَمَا مُحَمَّدٌ إِلَّا رَسُولٌ قَدْ خَلَتْ مِن قَبْلِهِ ٱلرُّسُلُ ۚ أَفَإِي۟ن مَّاتَ أَوْ قُتِلَ ٱنقَلَبْتُمْ عَلَىٰٓ أَعْقَـٰبِكُمْ ۚ وَمَن يَنقَلِبْ عَلَىٰ عَقِبَيْهِ فَلَن يَضُرَّ ٱللَّهَ شَيْـًٔا ۗ وَسَيَجْزِى ٱللَّهُ ٱلشَّـٰكِرِينَ

Muḥammad is not but a messenger. [Other] messengers have passed on before him. So if he was to die or be killed, would you turn back on your heels [to unbelief]? And he who turns back on his heels will never harm Allāh at all; but Allāh will reward the grateful.

Translation: Saheeh International

Tafsir

With regard to their being routed when it was rumoured that the Prophet had been killed and the hypocrites had said to the believers ‘If he has been killed go back to your previous religion’ the following was revealed Muhammad is only a messenger; messengers have passed away before him. …

Excerpt from Tafsir al-Jalalayn, commentary on 3:144, via Quran.com. The reader has the full commentary and 9 more tafsirs.