tie the knot

tie the knot (with sb) (to get married;|| {for a cleric or other authorized person} to perform a marriage ceremony, to unite a couple in marriage) — пожениться; связать себя узами брака; || сочетать кого-л. браком, провести церемонию бракосочетания

Example 1: So when are you two going to tie the knot? (yourdictionary.com)

Example 2: They should never have tied the knot, they were so much happier before they got married.

Example 3: She's planning to tie the knot with her American boyfriend next August.

Example 4: They asked their friend, who is a judge, to tie the knot. (yourdictionary.com)

Example 5: We tied the knot in a little chapel on the Arkansas border. (thefreedictionary.com)

Related vocabulary:
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lead sb to the altar (to marry)

Example 1: After a five-year courtship, he led her to the altar.