﴿ ٱلَّذِينَ ءَاتَيْنَٰهُمُ ٱلْكِتَٰبَ مِن قَبْلِهِۦ هُم بِهِۦ يُؤْمِنُونَ ﴾

“As for those unto whom We have vouchsafed revelation aforetime - they [are bound to] believe in this one [as well];”

(Those unto whom We gave the Scripture) the knowledge of the Scripture (before it) before the advent of Muhammad, Allah bless him and give peace, i.e. 'Abdullah Ibn Salam and his followers who were about 40 men, some of whom came from Historic Syria and others from Yemen, (they believe in it) they believe in Muhammad (pbuh) and in the Qur'an,