Among rational and moral creatures all higher life takes the form of a covenant. Generally, a covenant is an agreement between persons who voluntarily obligate and bind themselves to each other for the purpose of fending off an evil or obtaining a good. Such an agreement, whether it is made tacitly or defined in explicit detail, is the usual form in terms of which all humans live and work together. Love, friendship, marriage, as well as all social cooperation in business, industry, science, art, and so forth, is ultimately grounded in a
covenant, that is, in reciprocal fidelity and an assortment of generally recognized moral obligations.
It should not surprise us, therefore, that also the highest and most richly textured life of human beings, namely, religion bears this character. In Scripture "covenant" is the fixed form in which the relation of God to his people is depicted and presented. ..covenant is the essence of true religion.
Why should this be? First of all, because God is the Creator, man a creature; and with that statement an infinite distance between the two is given. No fellowship, no religion between the two seems possible; there is only difference, distance, endless distinctness. If God remains elevated above humanity in his sovereign exaltedness and majesty, then no religion is possible, at least no religion in the sense of fellowship.
...religion must be the character of a covenant. For then God has to come down from his lofty position, condescend to his creatures, impart, reveal, and give himself away to human beings; then he who inhabits eternity and dwells in a high and holy place must also dwell with those who are of a humble spirit (Isa. 57:15)... this set of conditions in nothing other than the description of a covenant.
This is what no religion has ever understood; all peoples either pantheistically pull God down into what is creaturely, or deistically elevate him endlessly above it. In neither case does one arrive at true fellowship, at covenant, at genuine religion. But Scripture insists on both: God is infinitely great and condescendingly good; he is Sovereign but also Father; he is Creator but also Prototype [ideal human pattern]. In a word, he is the God of the covenant.
~ Herman Bavinck, Reformed Dogmatics, II:568-70.