What does Proverbs 25:20 mean?

This verse speaks against careless, shallow reactions to another person's sorrow. All "proverbs" are general-case statements, not absolute rules for all situations. There are times when it makes sense to take off an article of clothing in the cold, such as if it's soaked with water. Songs can help cheer a mourning person, in the right situation. However, when someone is sad and discouraged, it's inappropriate to assume a simple song will make them feel better.

Trying to "comfort" someone with overly simple measures is not merely ineffective; it's insulting. Well-meaning comments might seem to minimize the experience. Offered to those in grief, such comments can magnify the suffering. Classic examples are phrases like, "there's a reason for everything," or "at least it wasn't something worse." Even if those sentiments are true, in a coldly logical sense, they're not usually helpful for the person grappling with tragedy.

"Soda" in this case probably refers to sodium carbonate, also referred to as "washing soda" or "natron." The original Hebrew word is nā'ter. This chemical was obtained from dry lake beds or other natural sources, and used for cleaning, preserving, and other tasks. The reaction of vinegar with soda produces an energetic reaction, but nothing else. Both the vinegar and the soda are lost, and what's left is much less useful. Trite attempts to cheer up those who mourn might spark a reaction, but not the one intended.

Job's misguided comforters did more harm than good by speaking volumes to him when he was burdened with physical pain and grief. Sometimes the best course of action to take when comforting a discouraged person is simply to sit with him in silence. Paul understood there is a time to grieve and a time to rejoice, and he kept the two in perspective. He writes in Romans 12:15: "Rejoice with those who rejoice, weep with those who weep." Only an insensitive person tries to rejoice with someone weeping, as if they could force a change in mood.