Plight your troth
Definition 1 of 1
Pro Tip 1/3Literary Use
Used in classic literature and historical contexts, not in modern conversations. 
In the novel, the knight plighted his troth to his lady.
Pro Tip 2/3Romantic Commitment
Emphasizes a deep romantic promise, more than just a casual agreement. 
With a kiss, they plighted their troth under the moonlight.
Pro Tip 3/3Solemn Vow
Describes a serious and earnest commitment, one that's not taken lightly. 
Before sailing, he vowed to return and plighted his troth to her.