Bede the Venerable — as excerpted in the Catena Aurea on Mark 1:2-3

“(ubi sup.) Being about to write his Gospel, Mark rightly puts first the testimonies of the Prophets, that he might notify to all, that what he should write was to be received without scruple of doubt, in that he shewed that these things were beforehand foretold by the Prophets. At once, by one and the same beginning of his Gospel, he prepared the Jews, who had received the Law and the Prophets, for receiving the grace of the Gospel, and those sacraments, which their own prophecies had foretold; and he also calls upon the Gentiles, who came to the Lord by publishing of the Gospel, to receive and venerate the authority of the Law and the Prophets; whence he says, As it is written in the prophet Isaiah, Behold, &c.”