The Jews had Pentecost before the Christians got hold of it. Many Christian feasts and customs are like that: we celebrate Christmas on the Roman feast of the sun's birthday, for instance, and many churches dedicated to the Virgin Mary are on the sites of more ancient temples to the Roman goddess Diana. We are the hermit crabs of the religious world, moving ourselves and all our belongings into other peoples' places and deciding to stay. Squatters: Nice place. If I stay here long enough, it'll be my house.
It was the Feast of Weeks, in Judaism: fifty days after Passover. And it was the day of offering to God the first fruits of the corn harvest, which probably means that the Hebrews, too, took on a more ancient fertility and harvest feast and made it their own. We have inherited and changed something they probably also borrowed and then altered to fit into their faith.
Christians look at Hindus and think them primitive because they have so many Gods, without realizing that they simply keep the files open on what we do, too: we appropriate the religious systems and images we find in the world and insert them into what we know of God. We find things and see how they fit. And after a while, they become Christian, part of the story of Jesus and faith in His saving works. Hindus don't have many gods: they have one God. But God has many manifestations in Hinduism, and each has a name and a colorful personality. People who pray in the name of the Father, the Son and the Holy Spirit should be able to relate to this better than we do.
But we don't. Borrowers though we may be, we act as if we were the sole custodians of the truth, and we act as if we invented it. As if "inspired by God" meant "plopped down in my lap without any history anywhere else, ever" As if we had God on a leash, like a pet. As if we had invented everything we think about God, and had no help with it.
And we think, oddly, that if it's true that Christmas was the sun's birthday once, or that Pentecost is a Jewish feast, it detracts from our store of truth. As if other faiths can be true only if ours is found false. As if God is so simple He can only do one thing at a time. We have a hard time letting history show in our faith, letting one thing ease into another through time and through the interaction of people and cultures. We don't remember that God works in mysterious ways, and that cultural assimilation can be one of them.
The Feast, as we have it, is all about the joining of cultures, about the many languages God uses with the human family. Barriers of language and distance break down before the mighty power of the Spirit. We have Pentecost today as a feast of understanding, among people and nations, a foretaste of a world in which we know one another.
And we have it as a feast of power. Not power we have made, but power we have received. The Spirit overcomes our limits, goes where we cannot go on our own, and takes us along.