(maybe only) You just need to add brake fluid in the brake master cylinder reservoir. If it is low on fluid, there is a sensor (electric wire connected on the side of the reservoir) that lights up the dashboard brake light. When you are driving, the brake fluid in the reservoir shakes, turning the light on and off when fluid is low.
Cause of low fluid, most of the time as Merlin2021 wrote "brake pads wear".
By the way, that is not ABS light. If it is ABS light, then there is something wrong with your Anti-lock Brake System. Not the brake pads or the brake fluid.
It is the light showing " Brake P & I ", Anti-lock Brake System shows letters "ABS" light.
Monday, September 3rd, 2007 AT 1:14 PM