Cyril of Jerusalem

To realize that Paul was filled with the Holy Spirit, and like him all the apostles, and all who after them believe in Father, Son and Holy Spirit, pay attention to the clear words of Paul himself.… "God who also stamped us with his seal and gave us the Spirit as a pledge."

Catechetical Lecture 17:32 ↗

Theophilus of Antioch

Wherefore such men have necessarily lost the wisdom of God, and have not found the truth. If you please, then, study these things carefully, that you may have a compendium and pledge of the truth.

Theophilus to Autolycus, Book III, Chapter XXX.—Why the Greeks Did Not Mention Our Histories ↗

Augustine of Hippo

I have learned from your letter, as well as from the statement of the bearer, that you ardently desire a letter from me, in the belief that it will bring you the greatest consolation. I must not refuse or delay this letter, but you will have to see what good you can draw from it. Let the faith and hope and charity, which are diffused through the hearts of the faithful by the Holy Spirit, be your consolation. We receive a little of it in this life as a pledge to make us learn how to long for its fullness. …

LETTER 92, To Italica ↗

Thomas Aquinas

But the union which is according to glory we do not yet have in reality, but in sure hope, inasmuch as we have a firm hope of attaining to this union. And we have a twofold certainty of hope resulting from the hope of this union. One is by a sign, the other by a pledge. The first is by an evident sign, which is of faith. Hence he says, he has put his seal upon us with the sign of Christian faith: "Put a mark on their foreheads" (Ez. …

Commentary on 2 Corinthians ↗