gentle as a lamb
(as) gentle as a lamb
Pleasant, caring, and calm. My rambunctious son is as gentle as a lamb with our cat. Mr. Stewart may seem crotchety, but he's as gentle as a lamb—he's actually helped me carry my groceries many times.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
*gentle as a lamb
Cliché [of someone] very gentle. (*Also: as ~.) Don't be afraid of Mr. Schaeffer. He may look fierce, but he's as gentle as a lamb. Lisa was gentle as a lamb when dealing with children.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.
gentle as a lamb
If someone is as gentle as a lamb, they are very kind and never become angry or aggressive. Brian was as gentle as a lamb and wouldn't hurt anyone. Verdy was as gentle as a lamb off the field but a raging lion on it.
Collins COBUILD Idioms Dictionary, 3rd ed. © HarperCollins Publishers 2012