"真诚的誓言"用英语可以翻译为"sincere pledge"或"sincere vow"。

这个词组来源于英语中的"sincere"和"pledge"或"vow"两个单词。"Sincere"意思是真诚的、诚恳的，而"pledge"和"vow"都指誓言、承诺。

下面是一些例句：

I make a sincere pledge to support you through thick and thin. 我发誓永远支持你，无论境况如何。
She made a sincere vow to devote her pfe to helping others. 她发誓把一生奉献给帮助他人。
He took a sincere pledge to always put his family first. 他发誓永远把家庭放在第一位。
She gave a sincere pledge to work hard and do her best in her new job. 她发誓会努力工作，尽力完成新工作。