That we must not Believe Everyone, and that we are Prone to Fall in Our Words
Lord, be thou my help in trouble, for vain is the help of man.(1) How often have I failed to find faithfulness, where I thought I possessed it. How many times I have found it where I least expected. Vain therefore is hope in men, but the salvation of the just, O God, is in Thee. Blessed be thou, O Lord my God, in all things which happen unto us. We are weak and unstable, we are quickly deceived and quite changed. 2. Who is the man who is able to keep himself so warily and circumspectly as not …
Thomas A Kempis—Imitation of Christ

Dialogue i. --The Immutable.
Orthodoxos and Eranistes. Orth.--Better were it for us to agree and abide by the apostolic doctrine in its purity. But since, I know not how, you have broken the harmony, and are now offering us new doctrines, let us, if you please, with no kind of quarrel, investigate the truth. Eran.--We need no investigation, for we exactly hold the truth. Orth.--This is what every heretic supposes. Aye, even Jews and Pagans reckon that they are defending the doctrines of the truth; and so also do not only the …
Theodoret—The Ecclesiastical History of Theodoret

Vehicles of Revelation; Scripture, the Church, Tradition.
(a) The supreme and unique revelation of God to man is in the Person of the Incarnate Son. But though unique the Incarnation is not solitary. Before it there was the divine institution of the Law and the Prophets, the former a typical anticipation (de Incarn. 40. 2) of the destined reality, and along with the latter (ib. 12. 2 and 5) for all the world a holy school of the knowledge of God and the conduct of the soul.' After it there is the history of the life and teaching of Christ and the writings …
Athanasius—Select Works and Letters or Athanasius

Psalms
The piety of the Old Testament Church is reflected with more clearness and variety in the Psalter than in any other book of the Old Testament. It constitutes the response of the Church to the divine demands of prophecy, and, in a less degree, of law; or, rather, it expresses those emotions and aspirations of the universal heart which lie deeper than any formal demand. It is the speech of the soul face to face with God. Its words are as simple and unaffected as human words can be, for it is the genius …
John Edgar McFadyen—Introduction to the Old Testament