He repeats this phrase to emphasize that this is something he would never do. AT: "Truly, truly, I would never" (See: [[rc://en/ta/man/translate/figs-idiom]])
This refers to destroying the city. This may be stated clearly. AT: "that I should swallow up or destroy your city" (See: [[rc://en/ta/man/translate/figs-ellipsis]])
Both of these phrases means to destroy. In the first phrase "destroying" is spoken of as if it were "swallowing." These may be combined. AT: "ruin or destroy the city" or "destroy" (See: [[rc://en/ta/man/translate/figs-doublet]] and [[rc://en/ta/man/translate/figs-metaphor]])