"Swear it!" rejoined he.

“发个誓吧！”他接茬说。

youdao

I swear it.

我发誓。

youdao

This tip sounds neurotic I know, but I swear it works.

这条建议听上去有点儿神经质，可我发誓这绝对有用。

youdao

"It was a tradition in Anglo-American culture to swear oaths on a Bible."

VOA: special.2009.01.19

And, I swear, it really contains Fresca.

我发誓，这里边装的真的是斯卡。

麻省理工公开课 - 固态化学导论课程节选

Expatriates swear it is one of the safest places in Africa.

FORBES: Magazine Article

We cannot swear it is genuine, but then neither perhaps could he: curious things do happen even at the upmarket end of what in those days was known as Fleet Street.

ECONOMIST: Inflation since 1900

Three seem to be Caucasian, one is African-American, and one appears to be of South Asian ethnicity (I would swear it is Aasif Mandvi of the Daily Show, you tell me).

FORBES: SEC Commissioner Aguilar Calls for More Boardroom Diversity