From Reagan’s biographer:

The carnage caused by Israeli bombings of Beirut was regularly highlighted on the nightly news, causing reactions within the Reagan administration that cut across the usual conservative-pragmatist divisions. The speechwriters were appalled; one of them, Landon Parvin, refused to write remarks for Reagan when Begin visited the White House for a chilly visit in June. On August 12, after Israeli planes had bombed Beirut for eleven consecutive hours, Deaver told Reagan he couldn’t continue to be part of “the killing of children” and intended to resign. Shultz and Clark had been sending similar signals to Reagan, albeit more diplomatically.

Reagan, also disgusted at the bombings, took the unusual step of calling Begin. “Menachem, this is a holocaust,” he told him.

In a voice that the aide who monitored the conversation said was “dripping with sarcasm,” Begin replied: “Mr. President, I think I know what a holocaust is.” But Reagan persisted. Begin called back twenty minutes later to say he had given the order to stop the bombings. After he hung up the phone, Reagan said to Deaver, “I didn’t know I had that kind of power.”

Biden during Israel’s 1982 invasion of Lebanon:

As Biden’s colleagues “grilled” Begin over Israel’s disproportionate use of force, including by targeting civilians with cluster bomb munitions, Begin said Biden “rose and delivered a very impassioned speech” defending the invasion. Begin said he was shocked at how passionately Biden supported Israel’s invasion when Biden “said he would go even further than Israel, adding that he’d forcefully fend off anyone who sought to invade his country, even if that meant killing women or children.”