For me, not giving money (especially when I have it) has been a process of allowing the addicts in my life to "learn" how to manage funds.
It is a big lesson to learn that spending all the money on the weekend may result in pbjs all week. And if that is where their drug use takes them, the faster they learn that, the better.
Perhaps you can view giving him money as "slowing his opportunity to find recovery". None of us would want to do THAT...
((hugs))