﴿ وَيَقُولُ ٱلَّذِينَ كَفَرُوا۟ لَسْتَ مُرْسَلًۭا ۚ قُلْ كَفَىٰ بِٱللَّهِ شَهِيدًۢا بَيْنِى وَبَيْنَكُمْ وَمَنْ عِندَهُۥ عِلْمُ ٱلْكِتَٰبِ ﴾

“And [if] they who are bent on denying the truth say [unto thee, O Prophet], "Thou hast not been sent [by God]", say thou: "None can bear witness between me and you as God does; and [none can bear witness as does] he who truly understands this divine writ.”

(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'.