hold by

hold by (something)

1. To grip or grasp someone by something in particular, such as a body part or an article of clothing. In this usage, a noun or pronoun is used between "hold" and "by." You need to hold Johnny by the hand when we cross the street. I held the stray dog by the collar while Paul went and looked for its owner.
2. To maintain something, typically something that one has agreed to. You need to hold by your contractual obligations to the company.
See also: by, hold
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.

hold someone or something by something

to grasp someone or something by a particular part. I held him by the shoulder while I talked to him. Donna held the dog by the collar.
See also: by, hold

hold by something

to stick by a promise. I hope that you will hold by our agreement. I will hold by everything I said.
See also: by, hold
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.
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References in classic literature ?
This seems to me, sir, as a man-rope; something that weak souls may hold by. Oh, sir, let old Perth now come and rivet these two hands together; the black one with the white, for I will not let this go.