Surah Al-Qasas — Ayah 53 (28:53)
وَإِذَا يُتۡلَىٰ عَلَيۡهِمۡ قَالُوٓاْ ءَامَنَّا بِهِۦٓ إِنَّهُ ٱلۡحَقُّ مِن رَّبِّنَآ إِنَّا كُنَّا مِن قَبۡلِهِۦ مُسۡلِمِينَ ٥٣
English translation (Saheeh International)
And when it is recited to them, they say, "We have believed in it; indeed, it is the truth from our Lord. Indeed we were, [even] before it, Muslims [i.e., submitting to Allāh]."
Brief commentary
When it is recited to them they say: “We believe it is the truth in which there is no doubt and which is revealed from our Lord. We were Muslims before this Qur’ān was revealed, due to our faith in what the Messengers before him brought”.