How to say no to picking up a shift for someone that always makes up horrific excuses & is a complete douchebag to everyone at work?

This person pretends to play manager because he has been a server at my work for 8+ years. He is incredibly bossy & everyone (including BOH) hates him at work. BOH will purposely push his tickets back & servers will make his area that he has to close messier as well.

He has a child & his parents are his babysitter for his kid. He will always try to get someone to cover their shift due to the parents or his wife being sick/in the hospital. He would never cover a shift for anybody else though.

He texted today & asked if i’d work his shift due to his father going to the hospital. He always does this to try to make people feel guilty into working for him.

How do I say no without sounding like a POS? It has also been very slow at work lately so I know I won’t make much money tonight if I did work for him regardless. TIA!