Gregory the Great
Catena Aurea · Lukasevangelium 14
For which of you, intending to build a tower, sitteth not down first, and counteth the cost, whether he have sufficient to finish it? Lest haply, after he hath laid the foundation, and is not able to finish it, all that behold it begin to mock him, Saying, This man began to build, and was not able to finish. Or what king, going to make war against another king, sitteth not down first, and consulteth whether he be able with ten thousand to meet him that cometh against him with twenty thousand? Or else, while the other is yet a great way off, he sendeth an ambassage, and desireth conditions of peace. So likewise, whosoever he be of you that for-saketh not all that he hath, he cannot be my disciple.
(ubi sup.) For when occupied in good works, unless we watch carefully against the evil spirits, we find those our mockers who are persuading us to evil. But another comparison is added proceeding from the less to the greater, in order that from the least things the greatest may be estimated. For it follows, Or what king, going to make war against another king, sitteth not down first, and consultelh whether he be able with ten thousand to meet him that cometh against him with twenty thousand?