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Young and inexperienced persons often can be remarkably wise, as in She's only six but she said, quite rightly, that Harry was afraid of the sitter? out of the mouths of babes, Mother said. This expression is a shortening and revision of expressions in the Old and New Testaments of the Bible. In Psalms 8:2, God ordains strength out of the mouth of babes and sucklings; in Matthew 21:16, praise comes from this source. Later generations changed strength and praise to wisdom.
American Heritage Idioms
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Phrase(s): Out of the mouths of babes (oft times come gems).
Prov. Children occasionally say remarkable or insightful things. • Mr. and Mrs. Doyle were quietly bickering in the kitchen when their seven-year-old daughter came in and said, "You guys should get counseling." After a surprised pause, Mrs. Doyle remarked, "Out of the mouths of babes." • Child: Don’t eat so much candy, Mommy. Candy is bad for your teeth. Mother: Out of the mouths of babes oft times come gems.
McGrawhill's American Idioms And Phrasal Verbs