Their reason? Israel's prime minister, Benjamin Netanyahu, denied entry into Israel for the two of them, owing to their public support of the Boycott, Divestments, and Sanctions movement, a global protest against the Israeli government's longtime mistreatment of Palestinians.
We give Israel more than $3 [billion] in aid every year. This is predicated on them being an important ally in the region and the only democracy in the Middle East. But denying a visit to duly elected members of Congress is not consistent with being an ally, and denying millions of people freedom of movement or expression or self-determination is not consistent with being a democracy.