You can see all the lectionary readings for the Trinity Sunday, Year A by clicking here. I have chosen to discuss the passage from the Gospel of Matthew.
This is a very short story. The disciples go to Galilee to meet Jesus at a mountain. They worship him there but some still have their doubts (they’re only human). Jesus tells them (I just can’t bring myself to paraphrase this):
All authority in heaven and on earth has been given to me. Go therefore and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit, and teaching them to obey everything that I have commanded you. And remember, I am with you always, to the end of the age.
This command from Jesus is known as the Great Commission—he is instructing the church to go on and share the Gospel with the whole world and teach others how to follow Jesus. Notice this is Trinity Sunday, when we celebrate the Trinity that is God—Father, Son, and Holy Spirit. The wording in the great Commission, “in the name of the Father and of the Son and of the Holy Spirit” is the same wording we use in creeds and at baptisms, confirmations, weddings, funerals. The Trinity is a mystery and a paradox—beyond our understanding, but we know God as three in one—God the Father and Creator; God the Son our Redeemer and Teacher; and the Holy Spirit, our Guide and Comforter.
We may not fully grasp the concept of the Trinity, but we can love and embrace the mystery on this day of celebration.