'As we have therefore'--that points a finger backwards to what has gone before. The Apostle has been exhorting to unwearied well-doing, on the ground of the certain coming of the harvest season. Now, there is a double link of connection between the preceding words and our text; for 'do good' looks back to 'well-doing,' and the word rendered 'opportunity' is the same as that rendered 'season.' So, then, two thoughts arise--'well-doing' includes doing good to others, and is not complete unless it does. The future, on the whole, is the season of reaping; the present life on the whole is the season of sowing; and while life as a whole is the seed-time, in detail it is full of opportunities, openings which make certain good deeds possible, and which therefore impose upon us the obligation to do them. If we were in the habit of looking on life mainly as a series of opportunities for well-doing, how different it would be; and how different we should be! Now, this injunction is seen to be reasonable by every man, whether he obeys it or not. It is a commonplace of morality, which finds assent in all consciences, however little it may mould lives. But I wish to give it a particular application, and to try to enforce its bearing upon Christian missionary work. And the thought that I would suggest is just this, that no Christian man discharges that elementary obligation of plain morality, if he is indifferent to this great enterprise. 'As we have an opportunity, let us do good to all.' That is the broad principle, and one application is the duty of Christian men to diffuse the Gospel throughout the world. I. Let me ask you to look at the obligation that is thus suggested. As I have said, well-doing is the wider, and doing good to others the narrower, expression. The one covers the whole ground of virtue, the other declares that virtue which is self-regarding, the culture which is mainly occupied with self, is lame and imperfect, and there is a great gap in it, as if some cantle had been cut out of the silver disc of the moon. It is only full-orbed when in well-doing, and as a very large constituent element of it, there is included the doing good to others. That is too plain to need to be stated. We hear a great deal to-day about altruism. Well, Christianity preaches that more emphatically than any other system of thought, morals, or religion does. And Christianity brings the mightiest motives for it, and imparts the power by which obedience to that great law that every man's conscience responds to is made possible.