John Chrysostom

"For the kingdom of God is not in word, but in power." By signs, saith he, not by fine speaking, we have prevailed: and that our teaching is divine and really announces the Kingdom of Heaven we give the greater proof, namely, our signs which we work by the power of the Spirit. If those who are now puffed up desire to be some great ones; as soon as I am come, let them shew whether they have any such power. And let me not find them sheltering themselves behind a pomp of words: for that kind of art is nothing to us.

Homily on 1 Corinthians 14 ↗

Cyprian

That we must labour not with words, but with deeds. In Solomon, in Ecclesiasticus: "Be not hasty in thy tongue, and in thy deeds useless and remiss." And Paul, in the first to the Corinthians: "The kingdom of God is not in word, but in power." Also to the Romans: "Not the hearers of the law are righteous before God, but the doers of the law shall be justified." Also in the Gospel according to Matthew: "He who shall do and teach so, shall be called greatest in the kingdom of heaven." Also in the same place: "Every one who heareth my …

Treatise XII Three Books of Testimonies Against the Jews ↗

Cosmas Indicopleustes

For the kingdom of God is not in word but in power; as if he said that the word of the kingdom of heaven surpasses all words, and that some are in vain puffed up while endeavouring to establish themselves by word. For that word only, which comes from the power of the Holy Spirit and from the signs which accompany it, merits belief.

The Christian Topography, Book 7 ↗

Thomas Aquinas

Thirdly, he assigns the reason, saying: The Kingdom of God does not consist in talk but in virtue; "Not everyone that says to me, Lord, Lord, shall enter the kingdom of heaven, but he that does the will of my Father (Matt 7:21).

Commentary on 1 Corinthians ↗