向他发誓的英语怎么说

向他发誓的英语是 "swear to him"。
这个短语来自于 "swear" 这个动词，意思是发誓，承诺，保证。"To him" 是介词短语，表示 "向他" 的意思。
下面是一些例句：
I swear to him that I will never lie to him again. 我向他发誓我不会再次对他撒谎。
She swore to him on her mother's grave that she would always love him. 她向他发誓，她会永远爱他。
He swore to him that he would never reveal the secret. 他向他发誓，他永远不会泄露这个秘密。