Some thoughts from Herman Bavinck on the Trinity:
“…the doctrine of the Trinity is of incalculable importance for the Christian religion. The entire Christian belief system, all of special revelation, stands or falls with the confession of God’s Trinity. It is the core of the Christian faith, the root of all its dogmas, the basic content of the new covenant.
…The profoundest question implicit in every Christian creed and system of theology is how God can be both one and yet three. Christian truth in all its parts comes into its own to a lesser or greater extent depending on how that question is answered. In the doctrine of the Trinity we feel the heartbeat of God’s entire revelation for the redemption of humanity. Though foreshadowed in the Old Testament, it only comes to light fully in Christ. Religion can be satisfied with nothing less than God himself. Now in Christ God himself comes out to us, and in the Holy Spirit he communicates himself to us. The work of re-creation is trinitarian through and through. From God, through God, and in God are all things. Re-creation is one divine work from beginning to end, yet it can be described in terms of three agents: it is fully accomplished by the love of the Father, the grace of the Son, and the communion of the Holy Spirit.
…We know ourselves to be children of the Father, redeemed by the Son, and in communion with both through the Holy Spirit. Every blessing, both spiritual and material, comes to us from the triune God. In that name we are baptized; that name sums up our confession; that name is the source of all the blessings that come down to us; to that name we will forever bring thanksgiving and honor; in that name we find rest for our souls and peace for our conscience. Christians have a God above them, before them, and within them. Our salvation, both in this life and in the life to come, is bound up with the doctrine of the Trinity…”
—Reformed Dogmatics, vol. II, pp. 333-334