Jesus is the central figure linking both Testaments and linking with both the Father and the Spirit. This is where Trinitarian theology comes from. Not from proof texts like the Great Commission, even though those are important, they echo the point. But the theology of it comes from the Old Testament. You have people like Bart Ehrman, and these other Jesus mythers and Ehrman is not a Jesus myther. But I'm using Ehrman because of his criticism of Christology, claiming that this theology of Christianity was invented by later church councils basically out of thin air, and that New Testament attestations to Jesus's deity were written late, just added arbitrarily. Both of those ideas show a deep profound ignorance of the Old Testament. The antecedent for all of this. Check this out!