Jesus, in John 6.45, says the writings of the prophets (note the plural), teaches that the future New Covenant will be different from the Mosaic Covenant. A direct quotation could be Is. 54.13 where it says: All your children will be taught by the Lord, and great will be their peace (NIV). The first verse of Isaiah 54, Paul quotes in Galatians 4.27: Be glad, barren woman, you who never bore a child; shout for joy and cry aloud, you who were never in labor; because more are the children of the desolate woman than of her who has a husband (NIV). Here, Paul notes a figurative use of Abraham’s two wives Hagar and Sarah as representing the major Two Covenants of the bible, old and new. Therefore, when Isaiah says in 54.13 that their children will all be taught of God, it connects with the promise in vs.1 that the desolate woman will have more children than the one who bore natural children. This speaks to the miraculous intervention of God in the adoption of children both of the Jews and Gentiles.

Also, Jesus’ quote in John 6.45 conceptually references Jer. 31.31-34 where it says that this “New” Covenant would no longer feature the priests and Levites instructing the people, but that everyone in this covenant will know the Lord on a personal basis, and thus be taught of Him. Here is an article about Tatian, an early Greek Christian.

How a Pagan Philosopher Came to Believe the Scriptures are from God – Canon Fodder