Imam Abu Ja`far bin Jarir said that Allah's statement,

﴿وَلَقَدْ أَنزَلْنَآ إِلَيْكَ ءَايَـتٍ بَيِّنَـتٍ﴾

(And indeed We have sent down to you manifest Ayat) means, "We have sent to you, O Muhammad, clear signs that testify to your prophethood.'' These Ayat are contained in the Book of Allah (Qur'an) which narrates the secrets of the knowledge that the Jews possess, which they hid, and the stories of their earlier generations. The Book of Allah also mentions the texts in the Books of the Jews that are known to only the rabbis and scholars, and the sections where they altered and distorted the rulings of the Tawrah. Since Allah mentioned all of this in His Book revealed to His Prophet Muhammad , then this fact alone should be enough evidence for those who are truthful with themselves and who wish to avoid bringing themselves to destruction due to envy and transgression. Further human instict testifies to the truth that Muhammad was sent with and the clear signs that he brought which he did not learn or acquire from mankind. Ad-Dahhak said that Ibn `Abbas said that,

﴿وَلَقَدْ أَنزَلْنَآ إِلَيْكَ ءَايَـتٍ بَيِّنَـتٍ﴾

(And indeed We have sent down to you manifest Ayat) means, "You recite and convey this Book to them day and night, although you are an Ummi (unlettered) who never read a book. Yet, you inform them of what they have (in their own Books). Allah stated that this fact should serve as an example, a clear sign and a proof against them, if they but knew.''