“The best thing in married life, for the sake of which everything ought to be suffered and done is the fact that God gives children and commands us to bring them up to serve Him. To do this is the noblest and most precious work on earth, because nothing may be done which pleases God more than the saving of souls. If the need were to arise, all of us should be ready to die in order to bring a soul to God. So you see how rich in good works the estate of marriage is. God lays souls into the lap of married people, souls begotten from their own body, on which they may practice all Christian works. For when they teach their children the Gospel, parents are certainly their apostles, bishops, and ministers.”

-- Martin Luther

“He who has children must think it is a pledge that God has committed to his charge; as if a man should commit his goods to his friend when he departs out of his house and gives him his key, or gives him his purse to keep.  Therefore fathers and mothers must keep their children as things committed to them by God upon this condition, that they have to render an account for them.  …
Besides this, fathers and mothers, and masters must consider that that which God has committed to their charge must be referred to God.  And therefore their children must be so taught, that they may be always God’s.  For as for the earthly fathers, they must not think that their children belong only to them, that God does not have constant and sovereign possession of them…”

 -- John Calvin -  From sermon on 1 Timothy 6:20-21.