Didascalicon, Book IV: the order and number of the divine books
Chapter IX. On the New Testament
As all the Scripture of the Old Testament can be called law, yet specially the five books of Moses are called the law; so generally the whole New Testament can be called Gospel, yet specially those four volumes, namely of Matthew, Mark, Luke and John, in which the deeds and sayings of the Saviour are plainly set forth, have deserved to be so called. Gospel is interpreted good news, because it promises eternal goods, not earthly felicity, as the Old Testament does according to the understanding of the letter.