keep (something) by
To keep some resource, especially money, in reserve for future use. It's good to reinvest your profits back into the business, but you should also keep some by in case of unforeseen hardships. We've been keeping extra funds by to help pay for the campaign.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
keep someone or something by someone
to make someone or something stay next to someone. Try to keep the twins by you until we have taken a few more pictures. Please keep this package by you until we are ready to present it.
keep something by
to keep something handy; to keep something in reserve, ready to be used. Keep this extra glue by in case you need it. This money had been kept by for just such an emergency.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.