The custom of the fermentum was first practiced as early as 120 A.D. A particle of the Eucharistic bread was carried by a minister of the Church from the bishop of one diocese to the bishop of another diocese. The receiving bishop would then consume the species at his next celebration of the Eucharist as a sign of the communion between the churches. The term fermentum was likely a reference to the Eucharist as the leaven of the Christian life, and the instrument by which Christians spread throughout the world were united in the one Body of Christ as a leaven to the world.