"It is evident that parents are laid under obligation not only to “train their children in the way that they should go, that when they are old they may not depart from it,” but also to “bring them up in the nurture and admonition of the Lord,” that is, (as the words certainly mean, and should be rendered in order to make them more intelligible,) “bring them up in the education and discipline of Christians,” that is, of those who “are the Lord's.” We are thus taught that our children by their baptism are devoted to the Lord, and become members of his church and kingdom, and that we are under obligation to bring them up as such, not merely by instructing them, and thoroughly imbuing their minds with Christian truth, but also by accustoming them to, and interesting them in, every part of Christian activity, devotedness, and zeal.
"It follows, therefore, as an undeniable inference, that it is incumbent upon every Christian, parent, teacher, and church, to see to it that the children of their charge are brought up as the Lord's,—as Christians,—as members of his visible church,—and therefore not only as those who ought to believe in him, and to know the doctrines that are of God, but as those who are bound also to love him, to serve him, to honor him, and to co-operate, according to their measure of ability and their sphere of influence, in the promotion of his glory, and the advancement of his cause. And as the term “Missionary” is employed to designate the work of making known “the glorious gospel of the blessed God” to those that know it not,—which is the great work and duty of the church, and of every Christian—it is therefore our manifest duty to bring up our children in a missionary spirit, and in a missionary practice.
"A missionary is one who is sent to preach the gospel to those that are “sitting in darkness and in the shadow of death,” whether abroad, or in our own country. To have a missionary spirit, is to be anxiously desirous that such missionaries should be sent, and the gospel made known to all that are “perishing for lack of knowledge.” And a missionary practice or habit, is the habit of carrying out this desire, first, by praying that such missionaries may be raised up “and sent forth by the Lord of the harvest, into every part of his vineyard ; secondly, by contributing as far as we can towards meeting the necessary expense of sending and supporting these missionaries, and supplying what is necessary to establish schools and print bibles, and other needful books; and, thirdly, by uniting with zeal in such efforts as will promote this spirit, and secure this habit…
"[It] is utterly impossible to have a missionary spirit, unless the heart is full of love and devotion to the cause of Christ; unless we can with pleasure give up everything however much it might add to our present comfort or happiness if it interferes with our duty; and unless we can bear all sorts of privations and trials that we may meet with in that narrow path. In short, to be able in all things to give up self, and think only how we can best serve God, promote his glory, and do his will, this alone is a real Missionary spirit. But this is the very spirit which must be shown, if we would see God's glory promoted, in every situation of life in which it may please him to place us. And hence we have seen some people who never went ten miles from home, do as much good in winning souls to Christ, as if they had left their country and travelled thousands of miles to reach the heathen. Missionaries, therefore, in the true sense of the word, but above all, a Missionary spirit, are needed everywhere! and in every condition of life."
-- from Thomas Smyth, "The Duty of Interesting Children in the Missionary Cause," in Complete Works of Thomas Smyth , Volume 7, pages 332, 345.