From the earliest times the Gospels were read and explained during Divine services; gradually certain portions, appropriate to the chief feasts and seasons of the year, were chosen and became a fixed part of the Mass. Thus, in Advent the Gospels relate to preparation for the coming of Christ; at Christmastide and the Epiphany, to the birth and childhood of Christ; in Lent, to penance and the Passion of Christ; at Eastertide, the last discourses of Jesus; after Pentecost, the nature and development of the Kingdom of God and the duties of its members. During the reading of the Gospel all stand as a mark of reverence for the Word of God and sign their foreheads, lips, and breast with the cross as a sign of readiness to believe, profess, and cherish its truths. The Gospel is read or sung after the Epistle by the celebrant, standing at the left side of the altar, as the people face it. The Last Gospel is that regularly read at the end of Mass (John 1); except on Vigils, days in Lent when the Mass of a feast is celebrated, and days of Special Commemoration.