﴿ 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.”

When those who are carried away by appearances, do not find signs in terms of miracles in the preacher of truth they are in doubt about the veracity of his message. But Truth is its own proof, however, its realization is possible for that person only who has developed in himself an eye which observes the reality by passing beyond outward appearances. Otherwise, one whose eyes are arrested by appearances will reject the truth, considering it baseless, though at that very time reason in its favour will be in existence right before him.