Okay, we have the volume forces:$\displaystyle \int \rho \overset{\rightharpoonup }{F}dV$

and the surface forces:$\displaystyle -\int p\overset{\rightharpoonup }{n}dA=-\int \nabla p \, dV$

If the fluid is in equilibrum:$\displaystyle \int \rho \overset{\rightharpoonup }{F}-\nabla pdV=0$

My question is how from the above you come to $\displaystyle \rho \overset{\rightharpoonup }{F}-\nabla p=0$