Deuteronomy(申命記) 20:7
Has anyone become pledged to a woman and not married her?
Deuteronomy(申命記) 28:30
You will be pledged to be married to a woman
to pledge是簡單的發誓。
to be pledged最常用的是承諾捐款或贊助:
One hundred dollars has been pledged to help the school children.
回到妳問的這句:
You must be pledged to keeping the secret
我相信這句是Chinglish,不是正常的英語。正常的英語是:
You must pledge to keep the secret.