The First Reading (Deut 4:32-34, 39-40) talks about the power and glory of God, who nonetheless, entered into a close and loving relationship with his people, Israel, and of the obligations and blessings that flow from such a relationship. This reading stresses the oneness of God.
In the Second Reading (Rom 8:14-17) this relationship is taken deeper; we are not just members of God’s people, but members of God’s family. We are God’s children. The Holy Spirit dwells within us and has made us co-heirs with the Son. This reading makes clear reference to the three persons in God.
The Gospel (Mt 28:16-20) also makes reference to the three persons of the Blessed Trinity. Jesus, who has total power over the whole universe, now empowers his apostles to preach the Gospel to the whole world.
The all-powerful Son of God promises to be with them (and by implication with us) until the end of time. The mission of the Church is to help all people to know and love God – the Father, the Son, and the Holy Spirit.