We affirm that the triune God is the archetype of all covenantal relations. All faithful theology and life is conducted in union with and imitation of the way God eternally is, and so we seek to understand all that the Bible teaches—on covenant, on law, on gospel, on predestination, on sacraments, on the Church—in the light of an explicit Trinitarian understanding.
This is, of course, the understanding of Reformed Covenant theology. Dr. Ligon Duncan, for example, teaches:
Covenant theology flows from the trinitarian life and work of God. God’s covenant communion with us is modeled on and a reflection of the intra-trinitarian relationships. The shared life, the fellowship of the persons of the Holy Trinity, what theologians call perichoresis or circumincessio, is the archetype of the relationship the gracious covenant God shares with His elect and redeemed people. God’s commitments in the eternal covenant of redemptive find space-time realization in the covenant of grace.
Dr. Duncan is restating the common Reformed truth articulated by Dr. Louis Berkhof in his Systematic Theology (p. 263):
The covenant idea developed in history before God made any formal use of the concept in the revelation of redemption. Covenants among men had been made long before God established His covenant with Noah and with Abraham, and this prepared men to understand the significance of a covenant in a world divided by sin, and helped them to understand the divine relation, when it presented man’s relation to God as a covenant relation. This does not mean, however, that the covenant idea originated with man and was then borrowed by God as an appropriate form for the description of the mutual relationship between between Himself and man. Quite the opposite is true; the archetype of all covenant life is found in the trinitarian being of God, and what is seen among men is but a faint copy (ectype) of this. God so ordered the life of man that the covenant idea should develop there as one of the pillars of social life, and after it had so developed, He formally introduced it as an expression of the existing relation between Himself and man.
So in Reformed Covenant Theology: God’s very being, as trinity, is covenantal.
We see this is true from several passages, not least the creation of humanity in the first chapter of the Bible:
So God created man in his own image,
in the image of God he created him;
male and female he created them (Genesis 1.27).
Marriage is not explicitly called a covenant until Malachi, but it is implied in Genesis. And we see here that marriage, as a covenantal relationship, reflects the image of God. God is a community. God is a covenant relationship between persons.
Likewise the Church reflects the unity of the Father and the Son in the Spirit. As Jesus prays:
Holy Father, keep them in your name, which you have given me, that they may be one, even as we are one… I do not ask for these only, but also for those who will believe in me through their word, that they may all be one, just as you, Father, are in me, and I in you, that they also may be in us, so that the world may believe that you have sent me. The glory that you have given me I have given to them, that they may be one even as we are one, I in them and you in me, that they may become perfectly one, so that the world may know that you sent me and loved them even as you loved me.
This unity is a unity in covenant. Thus, the Trinity is the foundational source and the church covenant reflects the Trinitarian unity in diversity.
Thus we see the concrete reality behind the affirmation “God is love” (First John 4.8, 16).
In the world today, embrace by Darwinian materialism, the most fundamental reality is violence. According to Christianity, the most fundamental reality is love in community. Unlike what is the case in unitarian religions, God was in loving relationship as an essential part of his nature. He did not need to create in order to have community and love. He created as an overflowing expression of community and love–Father, Son, and Holy Spirit.
Related: Affirming Justification by Faith Alone According to the Westminster Standards.