On August 15 the Orthodox Church celebrates the Feast of the Dormition of the Theotokos. We commemorate her death in this world of the Fall but recognize that through her bearing the Incarnate God in her womb she shared the blood of Christ before His Last Supper with His disciples. Thus not only poetically but theologically she shared in the salvation of Her Son, the reunion of divinity with humanity, from the beginning of His conception in her womb. The feasts of the Theotokos are thus all extremely Christological, yet recognizing the role humanity had to play in working out its salvation with the God who became incarnate.
“The Church’s celebration of the end of the earthly life of the Mother of God probably began in Jerusalem, where the tomb of Mary in the Gethsemane area is still a place of pilgrimage; by the sixth century the Feast was widely observed, and by about 600 A.D. the date had been fixed as 15th August. In current Orthodox practice the Feast is preceded by a fast from 1st August to the one day of Forefeast on 14th August; eight days of Afterfeast complete the festival. Two separate strands in the celebration can be seen: first, the death and burial of the Mother of God, and second, her Resurrection/Ascension/Assumption into heaven.” (John Baggley, Festival Icons for the Christian Year, pgs. 160-161)