He starts with 1 Cor. 7:20: ”Each one should remain in the condition (klesis) in which he was called” according to Gustaf Wingren in Luther on Vocation. Luther interprets klesis as vocation, “signifying one’s outer status,” not “confined to an occupation,” but including “biological orders” such as father, mother, son or daughter. In fact, “in anything that involves action, anything that concerns the world or my relationship with my neighbor, there is nothing…that falls in a private sphere lying outside of” vocation. So each person, then, always holds “a multitude of” vocations at the same time — as a father, husband, employer, and so on.
What are vocations for?
God designed them “to serve others.” Luther is not saying that a person in his vocation as a husband, for instance, ought to serve his wife (though I’m sure he’d not object). Rather, “at work in marriage is a power which compels self-giving to spouse and children.” (How then does Luther account for a dysfunctional marriage in which the husband does not love his wife?) To generalize: “what is effected through these orders [i.e., vocations] is not due to an inner transformation of the human heart.” Instead, God brings about his “work of love” on earth through these vocations — of marriage, of teacher and pupils, of government, and so on.
There is a direct connection between God’s work in creation and his work in these offices [i.e., vocations]. Silver and gold in the earth, growth in the creatures of the forests, the fruitfulness and unquenchable generosity of the soil, all is the ceaseless work of the God of creation, which goes forward through the labors of mankind. God creates the babes in the mother’s body — man being only an instrument in God’s hand – and then he sustains them with his gifts, brought to the children through the labors of a father and mother in their parental office.
So, God loves a child by sustaining him through the vocation of a father and mother. God loves a hungry man by giving him food through the vocation of a farmer. God loves me by giving me a song of encouragement through the vocation of song-writing and singing as carried out by Steven Curtis Chapman.
In sum, “care for one’s office is, in its very frame of reference on earth, participation in God’s own care for human beings.” Put differently, God loves the world by allowing us to fulfill our vocations, and through it, we get to love our neighbor with the love that comes from God.