Rejoice in the Lord alway: and again I say, Rejoice. -- Philippians 4:4 (KJV)
And again I say, Rejoice. Paul repeats the command like a man who knows the first pass will not be believed. It reads like a greeting card sentiment until you look at the address on the letter. This went to Philippi, the city that had him beaten bloody in its marketplace and jailed without a trial.
Roughly ten years separate that night from this letter, and Paul writes it from custody again, a soldier chained at his side in Rome while he waits on Caesar. So the church reading "rejoice in the Lord alway" could check the word against the record. Some of them were in Philippi when it happened; the jailer's family may have been sitting in the room as the letter was read aloud. They knew the man commanding it had already kept the command in their own town's prison, on their own town's worst night. Alway had covered their cell before it ever covered his.
A Few Lines Are Enough
In 2014 a nine-year-old boy named Willie Myrick was grabbed from his driveway in Atlanta and driven off by a stranger. From the back seat he sang one gospel chorus, "Every Praise," and kept singing it, the same few lines over and over, for hours, until the man pulled over and put him out unharmed. A child, a handful of words, nothing else in his hands.
That is roughly the size of what Paul and Silas had. No instrument, no audience they could see, no guarantee of morning, a couple of voices and the settled fact of who God is. "In the Lord" is where the rejoicing lives, and He is the one thing every cell, back seat, and hospital room has in common. So keep a song where you can reach it. Learn a few lines deep enough that they surface at the wrong hour. And when the command comes around and you cannot believe it the first time, take the letter's own advice: again.