My business partner asks money from me. how can I say no?

I am the brains of our small web development and design freelance partnership. I bring in tons of clients, we have agreed that no matter what the client can pay, my partner a developer will earn a fixed amount. luckily I pitch a reasonable price to earn more than my partner. not that my partner is paid less but what he receive is a big sum of money above the industry standards.

We had worked together in a corporation where in I asked and screened potential partners who are knowledgeable in tons of web development methods. so I chose him, in short we're not really super close buddies we just worked together for about 6months. when I partnered up with him, since he has a kid and some vices, he would ask money from me in a way like he's not ashamed to ask money from me and has different urgent excuses. one time he asked for more money for a project and I said ok. but after that he kept rushing the fee he's gonna earn from a project even if the client hasnt pay us yet. so I would just meet him halfway and pay him half. he never gets ashamed of doing this. whenever I tell him we have an upcoming project he wants to loan his upcoming fee from me. and Im not a lying kind of person. and I mean you can spot me lie-ing when I lie becoz i dont wanna lie to people. what can I say to him? any advice? thanks in advance.