The one living and true God is revealed, not as God absolute, but as God related, or as God subsisting from the beginning with certain internal relations; in a way admitting, in some sense, of mutual action and reaction; of a certain reciprocity of loving and being loved.
So we are to conceive of God as love. He is love. And his being love is not dependent on what may be called the accident or contingency of his having creatures to be loved. It springs out of the very necessity of his nature. It is his essential manner of being. Before the existence of any creature—before all time—God is love.
And he is not love potentially only, but actually: not capable of loving, but loving. He loves and is loved. He is love itself. He is not love quiescent, but love active and in exercise. He is so from all eternity. And he is so, and can only be so, in virtue of the eternal distinction of the divine persons in the Godhead, and the eternal relations which they sustain towards one another.
More particularly, it is in respect of the eternal relation of fatherhood and sonship that God is thus, from everlasting, love. It is chiefly in virtue of that relation that God is revealed as consciously, if I may so say, and energetically, love. From everlasting the Son is in the bosom of the Father. And the infinite, ineffable complacency subsisting between the Father and the Son in the Holy Ghost, is the primary exercise of that love which God is; that love which is of the essence of his nature.
It is thus that love in God has never been, properly speaking, the love of himself, or self-love. For there have ever been in the one undivided Godhead the holy three, Father, Son, and Holy Ghost, mutually loving and loved. And especially in the second person, and in the real and intimate relation of fatherhood and sonship between the first person and the second, the deep disinterestedness of the divine love is proved. The Father loveth the Son. The Spirit glorifieth the Son. For it is in the Son, as the Son, that the fatherly love of God flows forth in full stream. It flows forth to create and bless the countless multitude of intelligences who are, throughout eternity, to rejoice in calling the highest Father, in and with the Son.
Robert J. Candlish, The Fatherhood of God, pp. 67-69