The service we will celebrate on Palm Sunday has very ancient roots. Egeria, an early pilgrim, describes the observance of the day in Jerusalem in about the year 382, in a letter home to her sisters. So it was already established by then.*
In the version described by Egeria, it was an all day event. After Eucharist in the morning, people went home for lunch, but finished in time to meet the bishop near the top of the Mount of Olives. "There they participated in a service of hymns, antiphons and lessons." At three o'clock they went to the very top of the Mount for a similar service, and then Matthew's account of the procession into Jerusalem was read. Following that reading everyone processed down into the city to the site of Jesus' tomb, where they read the order of worship for evening. As people walked they "waved branches of palm or olive trees, sang psalms, and shouted the antiphon 'Blessed is he who comes in the name of the Lord.'"
The tradition spread throughout the church, appearing in Spain as early as the fifth century, and was adapted to work in various locations. In the Sarum rite the procession moved among various locations in the church for readings and psalms. The 1549 English prayer book didn't make much of the day, giving it the title simply "the Sunday next before Easter" and dispensing with the blessing of palms and procession. But by the 1950's the procession had become popular again in the United States and a form was provided for it in The Book of Offices (1960).
For our current Book of Common Prayer (published in 1979) a fairly succinct version was put together, which never the less contains most of the key elements of the earlier Jerusalem and Sarum observances. The service begins at some location outside the nave of the church. There the story of Jesus' entry into Jerusalem is read, and palms are blessed and distributed for the procession. The congregation then processes singing together to the nave. The earlier rites had a number of stops along the way, but we have just one stop where a collect is read before the procession continues.
Now as in the early rites, the Eucharistic service which follows has no further reference to the triumphal entry, but turns our attention to the betrayal and crucifixion. In the abrupt change from celebration to betrayal we follow the experience of Jesus and his disciples, who went from a triumphant arrival in Jerusalem and teaching in the temple to arrest, trial and crucifixion within 24 hours.
May you have a blessed Holy Week and a Joyous Easter.
The Rev. Dr. Thomas D. Harries
* Adapted from Marion J. Hatchet, Commentary on the American Prayer Book, Seabury, 1980