Fufilment

Sicut ergo nemo est credentium, dilectissimi, cui dona neganda sint gratiae, ita nemo est qui non sit Christianae debitor disciplinae: quai etsi remota est mysticae legis asperitas, voluntariae tamen observantiae crevit utilitas, dicente evangelista Joanne: Quia lex per Mosen data est, gratia autem et veritas per Jesum Christum est. Omnia enim quae secundum legem, sive in circumcisione carnis, sive in diversitatibus hostiarum, sive in sabbati observantia praecesserunt, Christum testificata, Christi sunt gratiam praelocuta. Et ipse est finis legis, non evacundo significationes ipsius, sed implendo. Qui licet idem sit autor veterum qui novorum, figuratarum tamen promissionum sacramenta mutavit, quia promissa perfecti, et denuntiatonibus cessationem imposuit, quoniam denuntiationibus advenit. In praeceptis autem moralibus nulla prioris Testamenti decreta reprobata, sed evangelico magisterio multa sunt aucta: ut perfectiora et lucidiora essent dantia salutem quam promittentia Salvatorem. Sanctus Leo Magnus, Sermo LXIII, De Passioni Domini XII Source: Migne PL 54.356a-b

As therefore there is no one faithful, most beloved, to whom the gifts of grace are denied, so there is no one who is not a debtor in the matter of Christian discipline, because even if the severity of the mystic Law has been put aside, yet the usefulness of its voluntary observance have grown, as the evangelist John says, 'Because the Law was given through Moses, but grace and truth through Jesus Christ.' 1 For everything according to the Law which preceded, whether in the circumcision of the flesh, or in the multitude of sacrifices, or in the keeping of the Sabbath, bore witness to Christ, and foretold the grace of Christ. And He is the end of the Law, 2 not annulling its meanings, but fulfilling them. For although He is the author of both the Old and of the New, yet He changed the figurative rituals of the promises, because He fulfilled the promises and ended their announcements, since the one who they announced came. But as for the moral precepts, no decrees of the previous Testament are rejected, but many are amplified by the teaching of the Gospel, so that the things which give salvation are more perfect and clearer than those which promised a Saviour. Pope Leo the Great, from Sermon 63, On The Passion of the Lord 1 Jn 1.17 2 Rom 10.4