From Thomas Aquinas’ Summa Theologiae, 3 q.46 a. 3:
Among means to an end, the more suitable is that whereby the various concurring means employed are themselves helpful to such end. But in this that man was delivered by Christ’s Passion, many other things besides deliverance from sin came together for man’s salvation.
- In the first place, man knows thereby how much God loves him, and is thereby stirred to love Him in return, and herein lies the perfection of human salvation; hence the Apostle says (Romans 5:8): “God commendeth His charity towards us; for when as yet we were sinners . . . Christ died for us.”
- Secondly, because thereby He set us an example of obedience, humility, constancy, justice, and the other virtues displayed in the Passion, which are requisite for man’s salvation. Hence it is written (1 Peter 2:21): “Christ also suffered for us, leaving you an example that you should follow in His steps.”
- Thirdly, because Christ by His Passion not only delivered man from sin, but also merited justifying grace for him and the glory of bliss, as shall be shown later (48, 1; 49, 1, 5).
- Fourthly, because by this man is all the more bound to refrain from sin, according to 1 Corinthians 6:20: “You are bought with a great price: glorify and bear God in your body.”
- Fifthly, because it redounded to man’s greater dignity, that as man was overcome and deceived by the devil, so also it should be a man that should overthrow the devil; and as man deserved death, so a man by dying should vanquish death.
Hence it is written (1 Corinthians 15:57): “Thanks be to God who hath given us the victory through our Lord Jesus Christ.” It was accordingly more fitting that we should be delivered by Christ’s Passion than simply by God’s good-will.