The book of the prophet Esaias. — The Law — i.e., the Pentateuch — was commonly written on one long roll. The other books, in like manner — singly or combined, according to their length — were written on rolls of parchment, and were unrolled from the cylinder to which they were fastened. Here, it is clear, Isaiah formed a roll by itself. It is a natural inference from the fact that it was given to Him, that it contained the prophetic lesson for the day. In the calendar of modern Jews, the lessons from Isaiah run parallel with those from Deuteronomy. The chapter which He read stands as the second lesson for the day of Atonement. We cannot prove that the existing order obtained in the time of our Lord’s ministry, but everything in Judaism rests mainly on old traditions; and there is therefore nothing extravagant in the belief that it was on the day of Atonement that the great Atoner thus struck what was the key-note of His whole work.
When he had opened the book. — Better, when He had unrolled.