Objection 1: It would seem that it was not fitting for man to be tempted by the devil. For the same final punishment is appointed to the angels' sin and to man's, according to Mt. 25:41, "Go [Vulg.: 'Depart from Me'] you cursed into everlasting fire, which was prepared for the devil and his angels." Now the angels' first sin did not follow a temptation from without. Therefore neither should man's first sin have resulted from an outward temptation.
Objection 2: Further, God, Who foreknows the future, knew that through the demon's temptation man would fall into sin, and thus He knew full well that it was not expedient for man to be tempted. Therefore it would seem unfitting for God to allow him to be tempted.
Objection 3: Further, it seems to savor of punishment that anyone should have an assailant, just as on the other hand the cessation of an assault is akin to a reward. Now punishment should not precede fault. Therefore it was unfitting for man to be tempted before he sinned.
On the contrary, It is written (Ecclus. 34:11): "He that hath not been tempted [Douay: 'tried'], what manner of things doth he know?"
He made us one with him when he chose to be tempted by Satan. We have heard in the gospel how the Lord Jesus Christ was tempted by the devil in the wilderness. Certainly Christ was tempted by the devil. In Christ you were tempted, for Christ received his flesh from your nature, but by his own power gained salvation for you; he suffered death in your nature, but by his own power gained glory for you; therefore, he suffered temptation in your nature, but by his own power gained victory for you.
If in Christ we have been tempted, in him we overcome the devil. Do you think only of Christ’s temptations and fail to think of his victory? See yourself as tempted in him, and see yourself as victorious in him. He could have kept the devil from himself; but if he were not tempted he could not teach you how to triumph over temptation. St Augustine