unknown part? broken/Missing bolt.

I have a 97 Jeep TJ with a 4" Suspension and a 2" body, the other day i noticed that a bar below my driver side door was swinging somewhat freely (about 2 inches to either side) but after a while it started to get really bad and now is swings as far as it can go to either side.. its banging against my drive shaft and i'm not sure what i need to fix it.



Any and all help is greatly appreciated



Thanks

-Zach