forswear oneself

例句：

1. 1.He forswore never to speak of it again.
   他发誓再也不提这件事了。
2. 2.She forswore to keep the secret.
   她发誓保守这个秘密。
3. 3. The king forswore to avenge his son's death.
   国王发誓要为他儿子的死报仇。