Congress holds the power of the purse. If congress appropriates the money, the president is legally obligated to spend that money for the reason that it was appropriated. (It’s called impoundment of appropriated funds.) This is why Trump was impeached the first time; he tried to withhold funding from Ukraine–before Russia invaded–that had already been appropriated by congress unless he got personal quid pro quo from Zelensky. Trump did not have the legal authority to withhold that funding, and hence was impeached for corruption.
Similarly, Biden can’t withhold money appropriated for Israel. He can, at best, veto the appropriations bill, which would send it back to Congress to be overridden. (Given that it passed 79-21 in the Senate–I can find the House vote tallies at the moment–it is highly likely that his veto would be overridden.) Should he do it anyways? Sure. But it would be purely symbolic.
The only options Biden has are diplomatic, which he is exercising. He could arguably use the military to invade, but congress would pull him up short on that very fast. Could he do more diplomatically? Yes, definitely. Can he unilaterally stop Israel? Categorically no.