Both of these questions mean the same thing and emphasize that God does what he says he will. These rhetorical questions can be translated as statements. Alternate translation: "He has never promised a thing without fulfilling what he promised. He has always done exactly what he said he would do." (See: [[rc://en/ta/man/translate/figs-parallelism]] and [[rc://en/ta/man/translate/figs-rquestion]])