Old And New

Dic mihi quid est inter Novum et Vetus Testamentum? Respondit: Vetus est peccatum Adae; unde dicit Apostolus: Regnavit mors ab Adam usque ad Moysen,  et reliqua. Novum est Christus de Virgine natus. Unde Propheta dicit: Cantate Domino canticum novum: quia homo novus venit; nova praecepta attulit, id est, Novum Testamentum Sanctus Isidorus Hispalensis, De Veteri et Novo Testamento Quaestiones, Quaestio I Source: Migne PL 83.201

Tell me, why is there an Old and a New Testament? The Old is the sin of Adam, whence the Apostle says, 'Death ruled from Adam to Moses,' 1 and the rest. The New is Christ born from the Virgin, whence the Prophet says, 'Sing to the Lord a new song,' 2 because the new man has come, bringing new commandments, that is, the New Testament. Saint Isidore of Seville, Questions on the Old and New Testaments, Question 1 1 Rom 5.14 2 Ps 149.1