How can one say that a man has attained purity? - When he sees all men as being good, and when none appears to him to be unclean and defiled - then he is indeed pure in heart.
Men who are leading a spiritual life see by the eyes of their heart how the devil lays his snares, how the angels guide us, and how the Lord, in His Sovereign power, allows the temptations, and how he comforts.
Blessed are the pure in heart, for they shall see God. Everything we do, our every objective, must be undertaken for the sake of this purity of heart. This is why we take on loneliness, fasting, vigils, work, nakedness. For this we must practice the reading of the Scripture, together with all the other virtuous activities, and we do so to trap and to hold our hearts free of the harm of every dangerous passion and in order to rise step by step to the high point of love.
Our holy fathers have renounced all other spiritual work and concentrated wholly on this one doing, that is, on guarding the heart, convinced that, through this practice, they would easily attain every other virtue, whereas without it not a single virtue can be firmly established.
