وَإِذَا يُتْلَىٰ عَلَيْهِمْ قَالُوٓا۟ ءَامَنَّا بِهِۦٓ إِنَّهُ ٱلْحَقُّ مِن رَّبِّنَآ إِنَّا كُنَّا مِن قَبْلِهِۦ مُسْلِمِينَ Qur’an Al-Qasas (28:53)Waitha yutla AAalayhim qaloo amanna bihi innahu alhaqqu min rabbina inna kunna min qablihi muslimeena
lit., ‘We had already been Muslims.’
There were Christians and Jews who recognised that Islam was a logical and natural development of Allah's revelations as given in earlier ages, and they not only welcomed and accepted Islam, but claimed, and rightly, that they had always been Muslims. In that sense Adam, Noah, Abraham, Moses, and Jesus had all been Muslims.