Nicene and Post-Nicene Fathers, Ser. II, Vol. XI:
The Works of John Cassian.: Chapter XXXVII. How the devil always lies in wait for our end, and how we ought continually to watch his head.

Chapter XXXVII.

How the devil always lies in wait for our end, and how we ought continually to watch his head. 806

For the subtle serpent is ever “watching our heel,” that is, is lying in wait for the close, and endeavouring to trip us up right to the end of our life. And therefore it will not be of any use to have made a good beginning and to have eagerly taken the first step towards renouncing the world with all fervour, if a corresponding end does not likewise set it off and conclude it, and if the humility and poverty of Christ, of which you have now made profession in His sight, are not preserved by you even to the close of your life, as they were first secured. And that you may succeed in doing this, do you ever “watch his head,” i.e. the first rise of thoughts, by bringing them at once to your superior. For thus you will learn to “bruise” his dangerous beginnings, if you are not ashamed to disclose any of them to your superior.

Footnotes

All through this chapter Cassian is alluding to Gen. iii. 15: “I will put enmity between thee and the woman and between thy seed and her seed; it shalt bruise thy head and thou shalt bruise his heel:” the last clause of which is rendered by the LXX. αὐτός σου τηρήσει κεφαλήν καὶ συ τηρήσεις αὐτοῦ πτέρναν, where the Vulgate has “Ipsa conteret caput tuum et tu insidiaberis calcaneo ejus.”