betroth

Short definition from Wiktionary

Verb

1. 1
   Of a man: to promise to take (a woman) as a future spouse; to plight one's troth to.
2. 2
   Often of a parent or guardian: to promise that (two people) be married to each other; specifically and chiefly, to promise that (a woman) be given in marriage to a man; to affiance.
3. 3
   Of God: to enter into a relationship with (believers, or the church as a whole); also, of a priest: to pledge (himself) to the church prior to being consecrated as a bishop.
4. 4
   To pledge or promise oneself to (a cause); to espouse; also (sometimes reflexive), to pledge or promise (oneself or one's efforts) to a cause or to do something.