John Chrysostom

"There is nothing covered, that shall not be revealed; nor hid, that shall not be known." Now what He saith is like this. It is indeed sufficient for your encouragement, that I also shared with you in the same reproach; I who am your Master and Lord. But if it still grieve you to hear these words, consider this other thing too, that even from this suspicion ye will soon be released. For why do ye grieve? At their calling you sorcerers and deceivers? …

Homily on the Gospel of Matthew 34 ↗

Jerome

For nothing is hidden that will not be revealed, and nothing secret that will not be known. And how in the present age the vices of many are not known? But about the future time it is written, when God will judge the secrets of men, and will illuminate the hiding places of darkness, and will make manifest the counsels of hearts. And the meaning is: Do not fear the cruelty of persecutors, and the rage of blasphemers, for the day of judgment will come, in which both your virtue and their wickedness will be demonstrated.

Commentary on Matthew ↗

Hilary of Poitiers

This refers to the day of judgment, which will make known the hidden conscience of our will and reveal to public knowledge those things that now seem obscure. Jesus is admonishing us, therefore, that we are not to fear our persecutors' threats or stratagems or power, because the day of judgment will reveal that these all were nothing and empty.

Commentary on Matthew 10.16 ↗

Thomas Aquinas

So have no fear of them... Here he exhorts them not to give in to tribulations. First, he strengthens them; secondly, he mentions a comparison; thirdly, he applies it to his purpose. He says, therefore, "they will persecute you," but have no fear, because you should fear evil only; but it is a great good to bear what the Lord has borne. Hence Paul to the Galatians (6:17): "I bear on my body the marks of Jesus." Nothing is covered that will not be revealed. This can be referred to the preceding or to what follows. …

Commentary on Matthew ↗