VII. The good works of Christians are only part of Christ's good works
This change, dearly-beloved, is the handiwork of the Most High, Who “works all things in all,” so that by the good manner of life observed in each one of the faithful, we know Him to be the Author of all just works, and give thanks to God's mercy, Who so adorns the whole body of the Church with countless gracious gifts, that through the many rays of the one Light the same brightness is everywhere diffused, and that which is well done by any Christian whatsoever cannot but be part of the glory of Christ.
This is that true Light which justifies and enlightens every man. This it is that rescues from the power of darkness and transfers us into the Kingdom of the Son of God. This it is that by newness of life exalts the desires of the mind and quenches the lusts of the flesh. This it is whereby the Lord's Passover is duly kept “With the unleavened bread of sincerity and truth” by the casting away of “the old leaven of wickedness” and the inebriating and feeding of the new creature with the very Lord.
For naught else is brought about by the partaking of the Body and Blood of Christ than that we pass into that which we then take, and both in spirit and in body carry everywhere Him, in and with Whom we were dead, buried, and rose again, as the Apostle says, “For you are dead, and your life is hid with Christ in God. For when Christ, your life, shall appear, then shall you also appear with Him in glory.” Who with the Father, etc.
Source: Sermons (New Advent)