The Catechism of the Catholic Church (paragraph 233) says, Christians are baptized in the name of the Father and of the Son and of the Holy Spirit: not in their names, for there is only one God, the almighty Father, his only Son and the Holy Spirit: the Most Holy Trinity. The Trinitarian formula is so central to the Christian sacrament of baptism (Mt. 28:18-20), and thus of justifying the sinner (Acts 2:38), that the Church rejects all other formulas as invalid, that is, not accomplishing the purposes of Baptism. This includes “the baptism of John“ (Acts 18:25), baptism in the “name of Jesus” (mistaking the euphemism for being baptized into Christ as a formula), or, in our own day, baptism “in the Name of the Creator, Redeemer and Sanctifier.”   The Holy Trinity is not specifically revealed in the Old Testament. This was reserved for the coming of Christ. However, the Trinity inevitably placed Its mark on creation and revelation to Israel, foreshadowing Christian revelation. Some examples are: Genesis 1:26 Then God said, “Let us make man in our image, after our likeness …”Genesis 3:22 Then the LORD God said, “Behold, the man has become like one of us, knowing good and evil …” In Genesis 18, three angels visit Abraham, who takes them to be God: 18:1 And the LORD appeared to him by the oaks of Mamre, as he sat at the door of his tent in the heat of the day. He lifted up his eyes and looked, and behold, three men stood in front of him. When he saw them, he ran from the tent door to meet them, and bowed himself to the earth, and said, “My lord, if I have found favor in your sight, do not pass by your servant. Abraham “negotiates” with the three angels over the fate of Sodom, saying, 18:27 “Behold, I have taken upon myself to speak to the Lord, I who am but dust and ashes. Such “theophanies” (manifestations of God), like that of the burning bush to Moses, tells us something about God who is spirit, as well as the Trinity, though only by analogy and without explicitly revealing the Triune nature of God.