III. As with the Saviour, so with us, the devil tries to make our very piety its own snare
But, dearly-beloved, doubt not that the devil, who is the opponent of all virtues, is jealous of these good desires, to which we are confident you are prompted of your own selves, and that to this end he is arming the force of his malice in order to make your very piety its own snare, and endeavouring to overcome by boastfulness those whom he could not defeat by distrustfulness. For the vice of pride is a near neighbour to good deeds, and arrogance ever lies in wait hard by virtue: because it is hard for him that lives praise-worthily not to be caught by man's praise unless, as it is written, “he that glories, glories in the Lord.”
Whose intentions would that most naughty enemy not dare to attack? Whose fasting would he not seek to break down? Seeing that, as has been shown in the reading of the Gospel, he did not restrain his wiles even against the Saviour of the world Himself. For being exceedingly afraid of His fast, which lasted 40 days and nights, he wished most cunningly to discover whether this power of abstinence was given Him or His very own: for he need not fear the defeat of all his treacherous designs, if Christ were throughout subject to the same conditions as He is in body. And so he first craftily examined whether He were Himself the Creator of all things, such that He could change the natures of material things as He pleased: secondly, whether under the form of human flesh the Godhead lay concealed, to Whom it was easy to make the air His chariot, and convey His earthly limbs through space.
But when the Lord preferred to resist him by the uprightness of His true Manhood, than to display the power of His Godhead, to this he turns the craftiness of his third design, that he might tempt by the lust of empire Him in Whom the signs of Divine power had failed, and entice Him to the worship of himself by promising the kingdoms of the world. But the devil's cleverness was rendered foolish by God's wisdom, so that the proud foe was bound by that which he had formerly bound, and did not fear to assail Him Whom it behooved to be slain for the world.
Source: Sermons (New Advent)