Venerable Isaac the Syrian. "Ascetical Homilies".
217. Therefore, the Lord leaves the reasons for humility and contrition of the heart in intensified prayer to His Saints, so that those who love Him will come closer to Him through humility. And often frightens them with the passions of their nature and the creeps of shameful and unclean thoughts, and often with reproaches, insults and slaps from people, sometimes with bodily illnesses and ailments, at other times, with poverty and lack of necessary things, then with excruciating strong fear, abandonment, obvious attacks of the devil, and various terrible incidents. And all this in order for them to have reasons for humility and not to fall into the sleep of sloth.