Our Semitic-oriented sacred authors would have a huge problem with our modern Greek-thinking habit of learning definitions of things before we've experienced them. Even worse, they'd cringe to discover that sometimes we actually limit and shape our experiences to fit snuggly into the definitions we've memorized.
This often is the case with today's celebration of the Trinity. The dogmatic definition of the Trinity - three persons in one God - didn't take shape as such until the Council of Nicea in 325 CE. That means none of our biblical writers could have used or even known the definition of the Trinity which we, as children, memorized and recited in our earliest catechism classes. Those who gave us our Christian Scriptures were more concerned with how people of faith related to and experienced God in their lives than theory were concerned with providing their readers with definitions and dogmatic statements.
Notice how Moses presents Yahweh in today's Deuteronomy passage. He does almost no defining. We simply hear a classic reminder of what Yahweh has done to build a relationship with the Israelites. "Did a people ever hear the voice of God speaking from the midst of a fire, as you did . . . ? Or did any god venture to go and take a nation for himself from the midst of another nation . . . which Yahweh your God did for you in Egypt before your very eyes?" God is how God relates.
Whenever relationships are formed, behavior changes. That's why Moses immediately reminds his people of the responsibilities they have that they didn't have before Yahweh stepped into their lives. " . . . You must now know and fix in your heart that Yahweh is God in the heavens above and on earth below, and that there is no other. You must keep Yahweh's statutes and commandments that I enjoin on you today . . . ."
As we hear in our Romans pericope, Paul believes something similar happens when followers of Jesus experience the Spirit of God working in their lives. According to the Apostle, such an encounter creates a whole new relationship with God. "Those who are led by the Spirit of God," Paul writes "are children of God. For you did not receive a spirit of slavery to fall back into fear, but you received a spirit of adoption, through which we cry, 'Abba, Father!'"
Just as freedom and a new relationship with Yahweh resulted from God breaking into the lives of a group of Hebrew slaves, so freedom and a new relationship with God results when Jesus' followers imitate his dying and rising. It's the same freedom and relating with God which Jesus experienced.
Writing with almost 20 years of additional experience of the risen Jesus working in the Christian community than Paul had, Matthew perceives that the force which entered his community's life when they began to die and rise with Jesus went beyond just Jesus. Though it seems Paul and his contemporaries baptized only "in the name of Jesus," Matthew recognizes that the Christian experience goes beyond just one person. Not only do we find a new "Trinitarian" formula for baptism - Father, Son and Spirit, but the church now aims far beyond the historical Jesus' original mission. The risen Jesus commands his followers, "Make disciples of all nations!" Though he writes for a Jewish-Christian community, Matthew's experience of Jesus has forced him to acknowledge that all people - not just Jews -should be invited to share in that experience.
Certainly nothing's wrong with learning definitions, as long as our definitions don't replace an experience which daily expands our understanding of God and God's people.