تعریف و معنای "{one's} word [is] {one's} bond"

What is the origin of the idiom "one's word is one's bond" and when to use it?

The phrase "one's word is one's bond" originated in 17th century England to describe relationships based on integrity and trust rather than written contracts. The saying is commonly invoked when requesting or giving assurances that promises will be kept, deals fulfilled as agreed, or that someone's testimony can be relied upon based on their reputation for high moral character and consistency between their words and actions.