8 But why does he say, “at noon-day”? The persecution is very hot; and thus the noon signifies the excessive heat....The demon that is “in the noon-day,” represents the heat of a furious persecution: for these are our Lord's words, “The sun was up; and because they had no root, they withered away:” and when explaining it, He applies it to those who are offended when persecution arises, “Because they have not root in themselves.” We are therefore right in understanding by the demon that destroys in the noon-day, a violent persecution.
Listen, beloved, while I describe the persecution, from which the Lord has rescued His Church. At first, when the emperors and kings of the world imagined that they could extirpate from the earth the Christian name by persecution, they proclaimed, that any one who confessed himself a Christian, should be smitten. He who did not choose to be smitten, denied that he was a Christian, knowing the sin he was committing: the arrow that flies by day reached him. But whoever regarded not the present life, but had a sure trust in a future one, avoided the arrow, by confessing himself a Christian; smitten in the flesh, he was liberated in the spirit: resting with God, he began peacefully to await the redemption of his body in the resurrection of the dead: he escaped from that temptation, from the arrow that flies by day.
“Whoever professes himself a Christian, let him be beheaded;” was as the arrow that flies by day. The “devil that is in the noon-day” was not yet abroad, burning with a terrible persecution, and afflicting with great heat even the strong. For hear what followed; when the enemy saw that many were hastening to martyrdom, and that the number of fresh converts increased in proportion to that of the sufferers, they said among themselves, We shall annihilate the human race, so many thousands are there who believe in His Name; if we kill all of them, there will hardly be a survivor on earth.
The sun then began to blaze, and to glow with a terrible heat. Their first edict had been, Whoever shall confess himself a Christian, let him be smitten. Their second edict was, Whoever shall have confessed himself a Christian, let him be tortured, and tortured even until he deny himself a Christian....Many therefore who denied not, failed amid the tortures; for they were tortured until they denied. But to those who persevered in professing Christ, what could the sword do, by killing the body at one stroke, and sending the soul to God?
This was the result of protracted tortures also: yet who could be found able to resist such cruel and continued torments? Many failed: those, I believe, who presumed upon themselves, who dwelt not under the defence of the Most High, and under the shadow of the God of Heaven; who said not to the Lord, “You are my lifter up:” who trusted not beneath the shadow of His wings, but reposed much confidence in their own strength. They are thrown down by God, to show them that it is He that protects them, He overrules their temptations, He allows so much only to befall them, as each person can sustain.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)