From the BBC:
The US has given $20bn (£15bn) to Ukraine, funded by the profits of seized Russian assets.
…
Funding the aid through frozen assets means Russia has to "bear the costs of its illegal war, instead of taxpayers," US Treasury Secretary Janet Yellen said.
He’s already given the money to the World Bank. Unfortunately, this means that it can’t be used for military purposes, as he would have had to get approval from Congress to do so.