What is the driving force for the filtration of blood by the renal corpuscle?

Higher pressure in glomerular capillaries than in the surrounding Bowman's capsule.

Explanation:

The renal corpuscle is composed of the capillary glomerulus and the Bowman's capsule that covers it, there is a space inside the capsule, Bowman's space, where the filtered liquid from the glomerulus passes. The glomerular pressure must be higher than in the surrounding Bowman's capsule, so in that way it forces the filtration and tends to expel fluid from the glomeruli, allowing the passage of water, small molecules of solute and ions.