Frank J. Wilstach, comp. A Dictionary of Similes. 1916.

Dumb

Dumb as Philomel.
—Anacreon

Dumb as an oyster.
—Anonymous

Dombe as any stoon.
—Geoffrey Chaucer

Doumb as a tree.
—Geoffrey Chaucer

Dumb as a senator.
—William Cowper

Dumb as death.
—Sydney Dobell

Dumb as a fish.
—Ben Jonson

Dumb as the grave.
—John Keats

Dumb as pillar-posts.
—George Meredith

Dumb as a mouse.
—English Proverb

As dumb as a dead cuddy.
—Scottish Proverb

Dumb as a dream.
—Algernon Charles Swinburne

Dumb and mighty, as a tree grows on a fruitful soil.
—Ivan Turgenev