As referred to this question Why can't charge be in a stable equilibrium in electrostatic field?, it is given that
Fig. 5–1.If $P_0$ were a position of stable equilibrium for a positive charge, the electric field everywhere in the neighbourhood would point toward $P_0$. Consider a tiny imaginary surface that encloses $P_0$, as in Fig. 5–1. If the electric field everywhere in the vicinity is pointed toward $P_0$, the surface integral of the normal component is certainly not zero. For the case shown in the figure, the flux through the surface must be a negative number. But Gauss’ law says that the flux of electric field through any surface is proportional to the total charge inside. If there is no charge at $P_0$, the field we have imagined violates Gauss’ law. It is impossible to balance a positive charge in empty space—at a point where there is not some negative charge. A positive charge can be in equilibrium if it is in the middle of a distributed negative charge. Of course, the negative charge distribution would have to be held in place by other than electrical forces.
Please explain the part which is denoted in bold. I have tried to comprehend the idea but did not get anything. My question is why the integral will be negative.I was also reading about this in the book Basic Laws of Electromagnetism, I encountered the same problem where is written:
the flux of E through the surface S is negative
Any help will be appreciated.
