It is impossible for the mind to remain undisturbed by thoughts, but anyone serious about the matter can certainly permit them entry or drive them away, and although their origin does not lie entirely under our control we can choose to approve of them and to adopt them.

... a Christian is quite certain to fall into the same sins which he condemns in another with merciless and inhuman severity, for 'a stern king will fall into misfortunes,' and 'one who stops his ears so as not to hear the weak, shall himself cry, and there shall be none to hear him' (Prov. 13:17; 21:13).

Perfection... is clearly not achieved simply by being naked, by the lack of wealth or by the rejection of honors, unless there is also that love whose ingredients the apostle described (cf. I Cor. 13) and which is to be found solely in purity of heart. Not to be jealous, not to be puffed up, not to act heedlessly, not to seek what does not belong to one, not to rejoice over some injustice, not to plan evil - what is this and its like if not the continuous offering to God of the heart that is perfect and truly pure, a heart kept free of all disturbance?

...we should realize that there are three sources for our thoughts - God, the devil, and ourselves.

The second request of the very pure soul is to see the coming of the Father's kingdom (cf. Mt. 6:10). What this means first of all is that each day Christ should reign among holy men. And this happens when the devil's power has been driven out of our hearts through the expulsion of sinful foulness and when God has begun to reign within us amid the good odors of virtue. With fornication vanquished, chastity rules; with anger overcome, peace is king; with pride under foot, humility is sovereign.

Let everybody know this. He shall be assigned to the place and to the service to which he gave and devoted himself in this life and he can be sure that in eternity he will have as his lot the service and the companionship which he preferred in this life. This is what the Lord means when He says, 'If anyone is my servant let him follow Me and where I am he will be there as my servant' (Jn. 12:26).

Men seized of the urge to have a knowledge of God and to be pure in mind devote all their gathered energies to this one task. While they still live in the corruption of the flesh they give themselves to that service in which they will persevere when the corruption has been laid aside. And already they come in sight of what the Lord and Savior held out when He said, 'Blessed are the clean of heart, for they will see God' (Mt. 5:8).