The Feast of Weeks, set down in the Book of Leviticus, was a "pilgrim feast." It required every Jewish male, able to do so, to travel to the the temple to offer a sacrfice. The sacrifice was to be two loaves of bread made of the grain gathered from the first harvest. This was an act of faith, showing the person trusted God to supply all their needs.  Just as the "pilgrims" of the Exodus trusted God to give them manna every day, so the believer of all time knew God would give them the sustenance they needed. It was called the "Feast of Weeks" because it was to be celebrated seven weeks and one day after the Passover.

Seven weeks plus one day is fifty days! That is the name by which we Christians that holy day -- Pentecost or "fiftieth day."

It was on this day that Jesus' disciples, devout Jews, came to the temple in accordance with God's command.