(They who disbelieve) in Muhammad (pbuh) and in the Qur'an (say: Thou art no messenger (of Allah)) O Muhammad, unless you bring us a witness who will testify that you are a messenger. Allah therefore said: (Say: Allah, and whosoever hath true knowledge of the Scripture) i.e. 'Abdullah Ibn Salam and his companions; it is also said that the reference here is to Asaf Ibn Barkhiyya, due to Allah's saying: (One with whom was knowledge of the Scripture) [27: 40]-and it is also said that this means: the one who has knowledge of the Scripture can explain the Qur'an-(is sufficient witness between me and you) that I am His Messenger and this Qur'an is His speech'.