I swear by Almighty God...

我以全能上帝之名发誓…

I swear by almighty God that I will tell the truth.

我向全能的上帝起誓，我以下所说句句属实。

Many people swear by vitamin C's ability to ward off colds.

很多人深信维生素C能预防感冒。

But a lot of people swear by it.

但是很多人对此坚信不疑。

Many women swear by both.

很多女性喜欢两种都用。