leave someone alone
Also, let someone alone. Refrain from disturbing or interfering with someone. For example, She'll manage very well if you just leave her alone, or Stop teasing the dog; let him alone. [c. 1400] Also see leave one in peace; let alone; let be.
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.