Sola Scriptura Teachings From The Early Church Fathers

Salvian the Presbyter (5th century): I need not prove by arguments what God Himself proves by His own words. When we read that God says He perpetually sees the entire earth, we prove thereby that He does see it because He Himself says He sees it. When we read that He rules all things He has created, we prove thereby that He rules, since He testifies that He rules. When we read that He ordains all things by His immediate judgment, it becomes evident by this very fact, since He confirms that He passes judgment. All other statements, said by men, require proofs and witnesses. God’s word is His own witness, because whatever uncorrupted Truth says must be the undefiled testimony to truth.
FC, Vol. 3, The Writings of Salvian, The Presbyter, The Governance of God, Book 3.1, pp. 68-69.

Nemesius of Emesa: But for us the sufficient demonstration of the soul’s immortality is the teaching of Holy Scripture, which is self-authenticating because inspired of God.
William Telfer, ed., The Library of Christian Classics, Vol. IV, Cyril of Jerusalem and Nemesius of Emesa: On the Nature of Man, Chapter 2 Of the Soul, p. 292

Lactantius (260-330): For it was not befitting that, when God was speaking to man, He should confirm His words by arguments, as though He would not otherwise be regarded with confidence: but, as it was right, He spoke as the mighty Judge of all things, to whom it belongs not to argue, but to pronounce sentence. ANF: Vol. VII, The Divine Institutes, Book III, Chapter I. See also FC, Vol. 49, The Divine Institutes, Book III, Chapter 1, pp. 165-166.

Clement of Alexandria (150 - c. 215): It will naturally fall after these, after a cursory view of theology, to discuss the opinions handed down respecting prophecy; so that, having demonstrated that the Scriptures which we believe are valid from their omnipotent authority, we shall be able to go over them consecutively, and to show thence to all the heresies one God and Omnipotent Lord to be truly preached by the law and the prophets, and besides by the blessed Gospel. ANF: Vol. II, The Stromata, Book IV, Chapter 1.

Athanasius: These are fountains of salvation, that they who thirst may be satisfied with the living words they contain. In these alone is proclaimed the doctrine of godliness. Let no man add to these, neither let him take ought from these. For concerning these the Lord put to shame the Sadducees, and said, ‘Ye do err, not knowing the Scriptures.’ And He reproved the Jews, saying, ‘Search the Scriptures, for these are they that testify of Me.’
Festal Letter 39

Basil of Caesarea: Enjoying as you do the consolation of the Holy Scriptures, you stand in need neither of my assistance nor of that of anybody else to help you comprehend your duty. You have the all-sufficient counsel and guidance of the Holy Spirit to lead you to what is right.
Letter 283

Cyril of Jerusalem: Even to me, who tell thee these things, give not absolute credence, unless thou receive the proof of the things which I announce from the Divine Scriptures. For this salvation which we believe depends not on ingenious reasoning, but on demonstration of the Holy Scriptures."
Catechetical Lectures 4:17