Objection 1. It would seem that the ceremonies of the Old Law did not cease at the coming of Christ. For it is written (Baruch 4:1): "This is the book of the commandments of God, and the law that is for ever." But the legal ceremonies were part of the Law. Therefore the legal ceremonies were to last for ever.
Objection 2. Further, the offering made by a leper after being cleansed was a ceremony of the Law. But the Gospel commands the leper, who has been cleansed, to make this offering (Matthew 8:4). Therefore the ceremonies of the Old Law did not cease at Christ's coming.
Objection 3. Further, as long as the cause remains, the effect remains. But the ceremonies of the Old Law had certain reasonable causes, inasmuch as they were ordained to the worship of God, besides the fact that they were intended to be figures of Christ. Therefore the ceremonies of the Old Law should not have ceased.
Objection 4. Further, circumcision was instituted as a sign of Abraham's faith: the observance of the sabbath, to recall the blessing of creation: and other solemnities, in memory of other Divine favors, as state above (102, 4, ad 10; 5, ad 1). But Abraham's faith is ever to be imitated even by us: and the blessing of creation and other Divine favors should never be forgotten. Therefore at least circumcision and the other legal solemnities should not have ceased.
On the contrary, The Apostle says (Colossians 2:16-17): "Let no man... judge you in meat or in drink, or in respect of a festival day, or of the new moon, or of the sabbaths, which are a shadow of things to come": and (Hebrews 8:13): "In saying a new (testament), he hath made the former old: and that which decayeth and groweth old, is near its end."
I answer that, All the ceremonial precepts of the Old Law were ordained to the worship of God as stated above (101, A1,2). Now external worship should be in proportion to the internal worship, which consists in faith, hope and charity. Consequently exterior worship had to be subject to variations according to the variations in the internal worship, in which a threefold state may be distinguished. One state was in respect of faith and hope, both in heavenly goods, and in the means of obtaining them--in both of these considered as things to come. Such was the state of faith and hope in the Old Law. Another state of interior worship is that in which we have faith and hope in heavenly goods as things to come; but in the means of obtaining heavenly goods, as in things present or past. Such is the state of the New Law. The third state is that in which both are possessed as present; wherein nothing is believed in as lacking, nothing hoped for as being yet to come. Such is the state of the Blessed.
In this state of the Blessed, then, nothing in regard to worship of God will be figurative; there will be naught but "thanksgiving and voice of praise" (Isaiah 51:3). Hence it is written concerning the city of the Blessed (Apocalypse 21:22): "I saw no temple therein: for the Lord God Almighty is the temple thereof, and the Lamb." Proportionately, therefore, the ceremonies of the first-mentioned state which foreshadowed the second and third states, had need to cease at the advent of the second state; and other ceremonies had to be introduced which would be in keeping with the state of divine worship for that particular time, wherein heavenly goods are a thing of the future, but the Divine favors whereby we obtain the heavenly boons are a thing of the present.
Reply to Objection 1. The Old Law is said to be "for ever" simply and absolutely, as regards its moral precepts; but as regards the ceremonial precepts it lasts for even in respect of the reality which those ceremonies foreshadowed.
Reply to Objection 2. The mystery of the redemption of the human race was fulfilled in Christ's Passion: hence Our Lord said then: "It is consummated" (John 19:30). Consequently the prescriptions of the Law must have ceased then altogether through their reality being fulfilled. As a sign of this, we read that at the Passion of Christ "the veil of the temple was rent" (Matthew 27:51). Hence, before Christ's Passion, while Christ was preaching and working miracles, the Law and the Gospel were concurrent, since the mystery of Christ had already begun, but was not as yet consummated. And for this reason Our Lord, before His Passion, commanded the leper to observe the legal ceremonies.
Reply to Objection 3. The literal reasons already given (102) for the ceremonies refer to the divine worship, which was founded on faith in that which was to come. Hence, at the advent of Him Who was to come, both that worship ceased, and all the reasons referring thereto.
Reply to Objection 4. The faith of Abraham was commended in that he believed in God's promise concerning his seed to come, in which all nations were to blessed. Wherefore, as long as this seed was yet to come, it was necessary to make profession of Abraham's faith by means of circumcision. But now that it is consummated, the same thing needs to be declared by means of another sign, viz. Baptism, which, in this respect, took the place of circumcision, according to the saying of the Apostle (Colossians 2:11-12): "You are circumcised with circumcision not made by hand, in despoiling of the body of the flesh, but in the circumcision of Christ, buried with Him in Baptism."
As to the sabbath, which was a sign recalling the first creation, its place is taken by the "Lord's Day," which recalls the beginning of the new creature in the Resurrection of Christ. In like manner other solemnities of the Old Law are supplanted by new solemnities: because the blessings vouchsafed to that people, foreshadowed the favors granted us by Christ. Hence the feast of the Passover gave place to the feast of Christ's Passion and Resurrection: the feast of Pentecost when the Old Law was given, to the feast of Pentecost on which was given the Law of the living spirit: the feast of the New Moon, to Lady Day, when appeared the first rays of the sun, i.e. Christ, by the fulness of grace: the feast of Trumpets, to the feasts of the Apostles: the feast of Expiation, to the feasts of Martyrs and Confessors: the feast of Tabernacles, to the feast of the Church Dedication: the feast of the Assembly and Collection, to feast of the Angels, or else to the feast of All Hallows.
Source: Summa Theologica (New Advent)