What should we ask of God, that we may experience purity and chastity?

St. Aphraphat the Persian sage invites us to pursue that which is conceived in our thoughts — purity of heart — and gives birth to chastity. He says, “First of all, the offering of Abel was accepted indeed before God through his purity of heart, and that of Cain was rejected (Gen. 4:3–5). And how was the matter known to us that the offering of Abel was accepted and that of Cain was rejected? And [how] did Abel understand that his offering was accepted and also again how did Cain know that his had been rejected? I will convince you about this as much as I can. But my beloved, you know that if an offering was acceptable before God, [then] it was distinguished by the fact that fire would descend from heaven and the offering was consumed by it. For when Abel and Cain offered their offerings together, living fire that was ministering before God (Ps. 104:4) came down and licked up the pure offering of Abel, and [since] that of Cain was impure it did not touch it. From there Abel understood that his offering was accepted, on the other hand Cain also realized that his was rejected. The fruits of Cain's heart demonstrated and witnessed about him that he was full of treachery when he killed his brother (Gen. 4:8). For to what his mind conceived, his hands gave birth. And the purity of the heart of Abel is his prayer.”⁸¹⁹