  We establish the physical process version of first law by studying small
perturbations of a stationary black hole with regular bifurcation surface in
Einstein-Gauss-Bonnet (EGB) gravity. Our result shows that when the stationary
black hole is perturbed by a matter stress energy tensor and finally settles
down to a new stationary state, the Wald entropy increases as long as the
matter satisfies null energy condition.
