And there was delivered unto him the Book of the Prophet Esaias. In the sabbath service there were two lessons read. The first was always taken from the Pentateuch (the Law). The five books of Moses were written on parchment, (usually) between two rollers, and the day's lesson was left unrolled for the reader's convenience.
The Prophets were on single rollers, no special portion being left open. It has been suggested that the great and famous Messianic passage read by our Lord was the lesson for the day. This is quite uncertain; indeed, it is more probable that Jesus, when the roll of Isaiah was handed to him by the ruler of the synagogue, specially selected the section containing this passage.