[en] The necessary stability criterion for equilibrium plasma configurations of arbitrary geometry is derived. At a low sound-to-Alfven velocity ratio the criterion turns into the Mercier criterion and at a vanishing shear, - into the Spies one. The criterion obtained imposes softer limitations on parameters of an equilibrium configuration in the small-shear range than the Mercier criterion. An approximate expression for the criterion for a toroidal configuration with a small curvature of the magn etic axis is presented