To be glad is a Christian duty. Many of us have as much religion as makes us sombre, and impels us often to look upon the more solemn and awful aspects of Christian truth, but we have not enough to make us glad. I do not need to dwell upon all the sources in Christian faith and belief, of that lofty and imperatively obligatory gladness, but I confine myself to the one in my text, 'Rejoicing in hope.' Now, we all know--from the boy that is expecting to go home for his holidays in a week, up to the old man to whose eye the time-veil is wearing thin--that hope, if it is certain, is a source of gladness. How lightly one's bosom's lord sits upon its throne, when a great hope comes to animate us! how everybody is pleasant, and all things are easy, and the world looks different! Hope, if it is certain, will gladden, and if our Christianity grasps, as it ought to do, the only hope that is absolutely certain, and as sure as if it were in the past and had been experienced, then our hearts, too, will sing for joy. True joy is _not_ a matter of temperament, so much as a matter of faith. It is _not_ a matter of circumstances. All the surface drainage may be dry, but there is a well in the courtyard deep and cool and full and exhaustless, and a Christian who rightly understands and cherishes the Christian hope is lifted above temperament, and is not dependent upon conditions for his joys. The Apostle, in an earlier part of this same letter, defines for us what that hope is, which thus is the secret of perpetual gladness, when he speaks about 'rejoicing in hope of the glory of God.' Yes, it is that great, supreme, calm, far off, absolutely certain prospect of being gathered into the divine glory, and walking there, like the three in the fiery furnace, unconsumed and at ease; it is that hope that will triumph over temperament, and over all occasions for melancholy, and will breathe into our life a perpetual gladness. Brethren, is it not strange and sad that with such a treasure by our sides we should consent to live such poor lives as we do?