Rejoice in the Lord always. Again I will say, rejoice! Philippians 4:4
“I want you to notice that this rejoicing is commanded. It is not a matter that is left to your option; it is not set before you as a desirable thing which you can do without, but it is a positive precept of the Holy Spirit to all who are in the Lord: “Rejoice in the Lord always.” We ought to obey this precept because joy in the Lord makes us like God. He is the happy God; ineffable bliss is the atmosphere in which He lives, and He would have His people to be happy.
You are commanded to rejoice because this is for your profit. Holy joy will oil the wheels of your life’s machinery. Holy joy will strengthen you for your daily labor. Holy joy will beautify you and give you an influence over the lives of others. It is upon this point I would most of all insist: we are commanded to rejoice in the Lord. If you cannot speak the gospel, live the gospel by your cheerfulness. For what is the gospel? Glad tidings of great joy, and you who believe it must show by its effect upon you that it is glad tidings of great joy to you. I do believe that a man of God—under trial, difficulty and affliction, bearing up, and patiently submitting with holy acquiescence, and still rejoicing in God—is a real preacher of the gospel, preaching with an eloquence that is mightier than words can ever be, and that will find its secret and silent way into the hearts of those who might have resisted other arguments. Do, then, listen to the text, for it is commanded from God: “Rejoice in the Lord always!”
When are we to be glad? “Rejoice in the Lord always,” that is, when you cannot rejoice in anything or anyone but God. When the fig tree does not blossom, when there is not fruit on the vine and no herd in the stall, when all withers, decays and perishes, when the worm at the root has made the gourd to die, then rejoice in the Lord. At the stake itself have martyrs fulfilled this word; they clapped their hands amid the fire that was consuming them. Therefore, rejoice in the Lord when you cannot rejoice in any other.
But also take care that you rejoice in the Lord when you have other things to rejoice in. When He loads your table with good things and your cup is overflowing with blessings, rejoice in Him more than in them. Forget not that the Lord your Shepherd is better that the green pastures and the still waters, and rejoice not in the pastures or in the waters in comparison with your joy in the Shepherd who gives you all. Let us never make gods out of our goods; let us never allow what God gives us supplant the Giver. Shall the wife love the jewels that her husband gave her better than she loves him who gave them to her? That is an evil love, or no love at all. So, let us love God first, and rejoice in the Lord always when the day is brightest, and multiplied are the other joys that He permits us to have.” (from Charles Spurgeon on Philippians 4:4)