“履行诺言”常见的英文表达是 “keep one's promise” 或 “fulfill one's promise”。
keep one's promise：强调持续遵守、不违背之前所做的承诺。例如：He always keeps his promises, so people trust him.（他总是履行诺言，所以人们信任他。）
fulfill one's promise：侧重于完成、实现之前许下的诺言。例如：She fulfilled her promise to help the poor children.（她履行了帮助贫困儿童的诺言 。）