There was plainly realized the number of this festival, which we read was figuratively foreshadowed in the Old Testament too, when it was ordered that at the end of seven weeks the bread of first fruits was to be offered to the Lord by the priests. This in very truth is recognized as having been offered to the Lord by the preaching of the apostles with which they are said to have exhorted the people on that day. This was the true bread of the first fruits, which was proffered at the beginning of the new teaching, when five thousand men were filled with the gift of its food and which consecrated to the Lord a Christian people newly born from the Jews.
[AD 435] John Cassian on Deuteronomy 16:9