If God once swore to non-believers that they would never enter into His rest–and it was on account of their lack of faith that they could not do so (cf. Hebrews 3:18-19)–how can mere bodily discipline, in the absence of faith, enable us to enter the rest of dispassion and the perfection of spiritual knowledge? We do in fact see many who because of this are unable to enter and to rest from their labors.
We must therefore be wary lest we possess an evil, unbelieving heart (cf. Hebrews 3:12), and because of this are thwarted of rest and perfection, in spite of our great labors. Otherwise we will be ceaselessly involved in the toils of the ascetic life and will always eat the bread of sorrow (cf. Psalm 127:2).
If a sabbath rest awaits us–the rest of dispassion and of perfect gnosis–let us through faith strive to enter into it, and not fall short of it because of our unbelief in the same way as those mentioned in the Bible (cf. Hebrews 4:9-11).
~Nikitas Stithatos
Prayerful Life 