Mark 1:2

Verse 2. In Isaias, the prophet. That in the ancient copies was read Isaias, and not Malachy, is confirmed by the Syriac version, and also by S. Irenæus, Origen, S. Jerom, and so forth It is also proved from an objection of Porphyrius, who says, Saint Mark mistook Isaias for Malachy. In the ordinary Greek copies at present, we read in the prophets, not naming either Isaias or Malachy. The words seem taken partly out of one, and partly out of the other. These words, behold I send my angel before thy face, who shall prepare thy way before thee, are found Malac. 3 verse 1. And the following words, a voice of one crying in the desert: prepare ye the way of the Lord, make straight his paths, are is Isaias, chapter 40, verse 3. Witham.—In the beginning of his gospel, Saint Mark alleges the authority of the prophets, that he might induce every one, both Jew and Gentile, to receive with willingness what he here relates, as the authority of the prophets so highly respected was very great. Saint John is here styled an angel, on account of his angelic life, and extraordinary sanctity; but what is meant by, who shall prepare thy way, is, that Saint John is to prepare the minds of the Jews, by his baptism and preaching, to receive their Messias. Theophylactus. See in Matthew 11:10.

“Behold”, from “ἰδοὺ”, means look at, take notice, observe, see, or gaze at. It is often used as an interjection.