I'm not going to split my commission with my coworker
Don't your coworkers deserve some of that commission too?
He's recently started working hard, but I'm the only one who has put enough work in. He's new to the company.
You should give some of that money to your coworker. I am sure he worked hard on that project and you failed to see it.
Nah, I'm the boss.
Boss or not, everyone who worked and contributed to the work needs to be compensated fairly. How would they feel doing all of this work to not be acknowledged from it? Rewarding them properly would make them want to stay in the company more.