cleave to

cleave to (one)

To have sex with one (typically a spouse) only, and no one else. I would never cheat on my husband—after all, I vowed to cleave to him until my dying day.
See also: cleave, to
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.

cleave to someone

to be sexually faithful, usually to one's husband. (Biblical. As in the traditional marriage ceremony, "And cleave only unto him.") She promised to cleave only to him for the rest of her life.
See also: cleave, to
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.
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References in classic literature ?
A man maun leave fether and mother (I'm yer fether), and cleave to his wife.
To be sure I might have known him, for every one was willing enough to tell me about him, and he himself was no accomplished hypocrite, but I was wilfully blind; and now, instead of regretting that I did not discern his full character before I was indissolubly bound to him, I am glad, for it has saved me a great deal of battling with my conscience, and a great deal of consequent trouble and pain; and, whatever I ought to have done, my duty now is plainly to love him and to cleave to him, and this just tallies with my inclination.
For of this be sure, blood will flow in rivers before the deed is done; many will still cleave to the king, for men worship the sun that still shines bright in the heavens, rather than that which has not risen.
It is just one person you shall need to cleave to and your life, business and leadership shall change forever.
Locate that one man or woman and cleave to him or her.
Once again, the best that can happen to anyone on earth is to discover and cleave to his or her purpose early in life.
The Liberal government, aided and abetted by ideologically driven courts, has launched a major attack on every Christian in Canada who accepts the Bible as the rule of faith and practice (for all who cleave to traditional marriage will be viewed as bigots and discriminators).
MACBETH: If you shall cleave to my consent, when 'tis,
'Cleave to my consent' means 'give me your support'; 'when 'tis' means 'when the time comes'; and 'honour,' as it is used here, seems to mean the sort of honor which Macbeth himself received when the King gave him the title of Thane of Cawdor.
"The tree is a good medium to cleave to as a reminder of things past and the things that we're losing."
The nitrogen to carbon bond can cleave to result in an amino radical and a formate radical.