Brewer's: Soft Words Butter no Parsnips
or “Fair words,” etc. Saying “Be thou fed” will not feed a hungry man. “Good words will not fill a sack.” To “butter parsnips” means also “dorer la pilule” (“soft words will not gild the pill of distress”).
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894