These two phrases share similar meanings. Together they emphasize that people will take offense at this "stone," which refers to Jesus. Alternate translation: "a stone or a rock over which people will stumble" (See: [[rc://en/ta/man/translate/figs-explicit]] and [[rc://en/ta/man/translate/figs-parallelism]] and [[rc://en/ta/man/translate/figs-metaphor]])
Here "the word" refers to the gospel message. To disobey means that they do not believe. "stumble because they are not believing the message about Jesus"