That He did on the cross and through the resurrection was the good work of God by which He has redeemed and restored all of creation, including you, back into a right relationship with God.
The resurrected Christ, who has all authority in Heaven and on Earth, also has His mind and His eye on the people who have gathered in your congregation this Sunday.
The celebration of Trinity Sunday–the only church festival specifically dedicated to a doctrine–reminds us of the necessity of confessing that the one God exists in three persons, Father, Son, and Holy Spirit.