This Sunday, we mark Trinity Sunday. Trinity Sunday is the only principal feast of the Church that commemorates a reality and doctrine rather than a person or event. Falling on the Sunday after Pentecost, we celebrate the Holy and Undivided Trinity as the final celebration, after Christ’s resurrection and ascension and the descent of the Holy Spirit at Pentecost.

The word “trinity” is actually not found in the scriptures, but in the Gospel according to Matthew, Jesus sends his disciples forth to baptize in the name of the Father, and the Son, and the Holy Spirit. From the day of our baptism, we are commissioned to go out into the world and show the love God as Jesus showed his disciples.

More than a doctrine, the Trinity expresses the heart of our faith: we have experienced the God of creation made known in Jesus Christ and with us always through the Holy Spirit. We celebrate the mystery of the Holy Trinity in word and sacrament, as we profess the creed, and as we are sent into the world to bear witness to our faith. We, as the body of Christ—the Church—are called to be a sign in the world of the Holy Trinity’s unity-in-diversity.

—Adapted from Washington National Cathedral