from Puritan At Heart
Christian, what bad news has Christ brought from heaven with him, that makes you walk with your arms folded and pensive countenance? To see a wicked man merry, or a Christian sad is alike uncomely. "A feast is made for laughter," says Solomon. I am sure God intended his people's joy in the feast of the Gospel; mourners were not to sit at God's table (Deut. 26:14).
Truly the saint's heaviness reflects unkindly upon God himself. We do not commend his cheer, if it does not cheer us. What saith the world? "The Christian's life is but a melancholy walk," thinks the carnal wretch, "it is a dry feast they sit at, where so little wine of joy is drunk." And will you confirm them in this their opinion, Christian? Shall they have your example to produce against Christ and his Word, which promises peace and joy to all that will come to this feast?...
Now will they believe 'tis good news indeed the Gospel brings, when they can read it in your cheerful lives; but when they observe Christians sad with this cup of salvation in their hands, truly they will suspect the wine in it is not so good as the preachers commend it... O Christians, let the world see you are not losers in your joy, since you have been acquainted with the Gospel; give them not cause to think by your uncomfortable walking, that when they become Christians, they must bid farewell to all joy, and resolve to spend their days in the hour of mourning.
--William Gurnall, "A Homiletic Encyclopedia, pp. 757."
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I fail in this area daily and for years, I have a long way to grow.