Hilary of Poitiers (c 315-67):
"The Apostle who was chosen not of then nor through man, but through Jesus Christ, to be the teacher of the Gentiles, expounds in language as express as he can command the secrets of the heavenly Dispensations. He who had been caught up into the third heaven and had heard unspeakable words, reveals to the perception of human understanding as much as human nature can receive. But he does not forget that there are things which cannot be understood in the moment of hearing. The infirmity of man needs time to review before the true and perfect tribunal of the mind, that which is poured indiscriminately into the ears. Comprehension follows the spoken words more slowly than hearing, for it is the ear which hears, but the reason which understands, though it is God Who reveals the inner meaning to those who seek it. We learn this from the words written among many other exhortations to Timothy, the disciple instructed from a babe in the Holy Scriptures by the glorious faith of his grandmother and mother: Understand what I say, for the Lord shall give thee understanding in all things. The exhortation to understand is prompted by the difficulty of understanding. But God’s gift of understanding is the reward of faith, for through faith the infirmity of sense is recompensed with the gift of revelation. Timothy, that ‘man of God’ as the Apostle witnesses of him, Paul’s true child in the faith, is exhorted to understand because the Lord will give him understanding in all things: let us, therefore, knowing that the Lord will grant us understanding in all things, remember that the Apostle exhorts us also to understand."
Source:NPNF2: Vol. IX, On the Trinity, Book XI, §23
For an excellent compilation of quotes of the Church fathers teaching on the primacy, sufficiency and ultimate authority of Scripture, get a copy of Holy Scripture:The Ground and Pillar of Our Faith Vol III- The Writings of the Church Fathers Affirming the Reformation Principle of Sola Scriptura.