Hamas’s original 1988 charter explicitly calls for the destruction of Israel, stating that "Israel will exist and will continue to exist until Islam will obliterate it" and frames the conflict as a religious duty, advocating for the elimination of Israel through jihad. The charter also references violent hadiths and rejects any peaceful solution or recognition of Israel.
In 2017, Hamas released a new policy document that softened some language, distinguishing between Jews and Zionists and accepting a Palestinian state along 1967 borders as a "formula of national consensus." However, it still rejects the legitimacy of Israel and maintains the goal of "liberation of Palestine, from the river to the sea," which includes all of present-day Israel.
The bottom line is that "from the river to the sea" is a softened way of saying "obliterate Israel" according to Hamas' charter.