St. Clement of Alexandria: We must not live as if there were no difference between right and wrong...

We must not live as if there were no difference between right and wrong, but, to the best of our power, must purify ourselves from indulgence and lust and take care for our soul which must continually be devoted to the Deity alone. 

For when it is pure and set free from all evil the mind is somehow capable of receiving the power of God and the divine image is set up in it. "And everyone who has this hope in the Lord purifies himself," says the Scripture, "even as he is pure.

St. Clement of Alexandria