The expression appears in the law, but is undefined! I don't believe anybody actually ever bothered to define it. There is a basic contradiction between being "Jewish" and "Democratic". Suppose the number of Arabs becomes larger than the number of Jews, would the state still remain Jewish? In what sense? So far, the Supreme Court has to grapple with the meaning whenever a case comes up. For example, by law a party or an individual cannot run for elections if they deny the nature of Israel as Jewish and Democratic. Do the Islamist Knesset members violate this? According to the Court, no. Does the Communist Party, which rejects differences between people on the basis of ethnicity and considers differences based on economics more fundamental, is elligible to run? I don't think this was ever in question. Had I been a Palestinian wishing to attain Israeli citizenship I would have agreed to pledge this meaningless pledge.
Shaffir to Herzog: Opposition failed to show leadership in political battles against PM (Haaretz)
from the article: I am not declaring loyalty