Adam Clarke's Commentary on the Bible

Verse 13 (James 5:13)

Is any among you afflicted? let him pray - The Jews taught that the meaning of the ordinance, Leviticus 13:45 , which required the leper to cry, Unclean! unclean! was, "that thus making known his calamity, the people might be led to offer up prayers to God in his behalf," Sota, page 685, ed. Wagens. They taught also, that when any sickness or affliction entered a family, they should go to the wise men, and implore their prayers. Bava bathra, fol. 116, 1.

In Nedarim, fol. 40, 1, we have this relation: "Rabba, as often as he fell sick, forbade his domestics to mention it for the first day; if he did not then begin to get well, he told his family to go and publish it in the highways, that they who hated him might rejoice, and they that loved him might intercede with God for him."

Is any merry? let him sing psalms - These are all general but very useful directions. It is natural for a man to sing when he is cheerful and happy. Now no subject can be more noble than that which is Divine: and as God alone is the author of all that good which makes a man happy, then his praise should be the subject of the song of him who is merry. But where persons rejoice in iniquity, and not in the truth, God and sacred things can never be the subject of their song.

- Adam Clarke's Commentary on the Bible