The author uses this question to teach his readers. Alternate translation: "And it was to those who disobeyed that he swore they would not enter his rest." (See: [[rc://en/ta/man/translate/figs-rquestion]])
The peace and security provided by God are spoken of as if they were rest that he can give, and as if they were a place to which people could go. Alternate translation: "they would not enter the place of rest" or "they would not experience his blessings of rest" (See: [[rc://en/ta/man/translate/figs-metaphor]])