Why do static fluids always exert a force perpendicular to the surface?

In a static fluid, the molecules are in constant random motion, colliding in all directions. When a surface is placed within the fluid, the pressure at any point arises due to the weight of the fluid above it and molecular collisions. These collisions exert forces equally in all directions, but the net force on any element of the surface is always perpendicular. This occurs because, in a static state, no tangential motion exists within the fluid. Hence, pressure in a liquid acts uniformly in all directions but is always exerted perpendicularly to any contact surface.

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