الخل
A fermented condiment praised as a good relish for the table, and combined with honey (oxymel) as a digestive tonic.
نِعْمَ الْأُدُمُ الْخَلُّ
“What an excellent condiment vinegar is.” (meaning, not a literal translation)
This hadith is reported in the context of household simplicity and gratitude for what's available, rather than as part of an extended medical narrative — one of the more straightforwardly authenticated food-related sayings, praising a humble, always-available condiment rather than expecting elaborate provisions.
Ibn al-Qayyim recommends vinegar to counter honey's warming effect for those with a bilious temperament, and as a base for oxymel (sakanjabeen) — honey, vinegar, and water — to settle the stomach after rich or date-heavy meals. He describes vinegar as cooling and drying within the classical humoral framework, useful for reducing excess bile and counteracting the effects of overly rich food when taken as a regular condiment rather than a concentrated remedy.
Some modern research has examined vinegar's (acetic acid's) effects on post-meal blood sugar response and appetite. Noted here as separate modern context, not validation of the classical humoral framework it was originally described within.