plight troth to
plight (one's) troth to (someone)
To bind oneself to someone in marriage. This archaic phrase, still sometimes used in modern writing for stylistic effect, employs the obsolete words "plight" ("to pledge") and "troth" ("truth"). There are some practical matters that people rarely consider when they decide to plight their troth to each other. I'll plight my troth to whomever I so please, Mother—the decision is not yours!
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
plight one's troth to someone
to become engaged to be married to someone. (Literary or jocular.) I chose not to plight my troth to anyone who acts so unpleasant to my dear aunt. Alice plighted her troth to Scott.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.