make a vow
take a vow

We've already taken a vow to stay friends through it.

She then took a vow of silence and removed herself from public activity.

At an early age, he took a private vow of chastity.

Well, he thought, it isn't as if I took a vow, or anything.

I'm not suggesting you take a vow to be single.

Of course, no one could have got near him if he had not taken a vow never to kill again.

And even if he didn't take a vow of chastity, nothing's going to happen between us.

Now let's just take a vow that nothing erotic will ever pass between us.

He who had taken a simple vow knew well enough how things can twist and change.

The truth is that I have taken a certain vow.