As long as the foxes and birds {i.e. the distractions and lusts of this world} have holes and dens in us, how can Christ enter (cf. Lk 9:58)? Where can He rest? What communion is there between Christ and Belial? (2 Cor. 6:15). For He lodgeth in the saints, and dwelleth in them that love Him; but withdraws from the impure and the unclean. Expel the beasts, hunt out the foxes, drive away the birds, free thy heart from their impurity in order that the Son of man may find a place in thee to lay His head; even the Word of God Who was incarnate and became man. For light has no concord with darkness, nor the impure with the holy. It is a thing altogether incredible for there to be stored up in one vessel perfume and filthiness...
Let us, therefore, cleanse ourselves from every stain of the flesh, and of the spirit. Let us put to death those members which are upon the earth (2 Cor 7:1, Col 3:5)... Let our heart be holy and unpolluted, as far as is possible and may be. For so shall we follow Christ, according as He giveth us the grace and He will dwell joyfully in us. For then He will have where to lay His head, and rest in us as in saints. For it is written: Become ye holy, because I am holy (1 Pet. 1:16).
(Commentary on the Gospel of St. Luke, p. 248)
For earnestly to follow Christ is confessedly profitable to salvation; but he who wishes to be counted worthy of so great glory must, I say, bear his cross. And what is it to bear the cross? It is to die unto the world, by denying its empty distractions, and manfully abandoning a carnal and pleasure-loving life. For it is written: Love not the world; neither the things that are in the world, for every thing that is in the world is the lust of the body, and the lust of the eyes, and the pride of life (1 John 2:15-16). And again, Know ye not that the love of the world is enmity unto God? Whosoever, therefore, would be a friend of the world is found God's enemy. (James 4:4).
(Commentary on the Gospel of St. Luke, p. 247)