Collins Chinese Dictionary Plus (3rd edition), 2011:
vow [vau]
I n
[c]
誓言 shìyán [个 gè]
II vt
▶ to vow to do sth 发(發)誓做某事 fāshì zuò mǒushì
- to take or make a vow to do sth
立誓要做某事 lìshì yào zuò mǒushì
- to vow that…
立誓… lìshì…