Augustine of Hippo

"And while I was musing, the fire burned" [Psalm 39:3]....I reflected on the words of my Lord, "Thou wicked and slothful servant, you ought to have put My money to the exchangers, and I at My coming should receive it again with usury." [Matthew 25:26-27] And that which follows may God avert from those who are His stewards! Bind him hand and foot, and let him be cast into outer darkness; [Matthew 25:30] the servant, who was not a waster of his master's goods, so as to destroy them, but was slothful in laying them out to improve them. …

Exposition on Psalm 39 ↗

Thomas Aquinas

But the remedy of interior charity is applied; and therefore he says: "My heart grew hot within me," that is, the heat of charity was stirred up in my heart. Prov. 6: "Can a man hide fire in his bosom, and his garments not burn?" So it is impossible that a man should hide the words of God when his heart is inflamed with charity. Ps. 119: "Your word is a fire," etc. …

Exposition on the Psalms of David ↗

Bernard of Clairvaux

A soul entangled in many sins can prepare for itself a certain ointment once it begins to reflect on its behavior, and collects its many and manifold sins, hems them together and crushes them in the mortar of its conscience. It cooks them, as it were, within a breast that boils up like a pot over the fire of repentance and sorrow, so that it can exclaim with the Prophet: "My heart became hot within me. …

Sermons on the Song of Songs, Sermon 10 ↗