On How the House of the Soul is Built, Second Excerpt:

The roof is charity, which is the completion of virtue as the roof completes the house. After the roof comes the crowning of the dwelling place; and what is this crowning? In the Law it is written, 'If you build yourself a house and make it your dwelling place, put a crown round your house (i.e. railings around the flat roof) lest your children fall from the roof'. The crown is humility. For that is the crown and gaurdian of all virtues. As each virtue needs humility for its acquisition- and in that sense we said each stone is laid with the mortar of humility- so also the perfection of all the virtues is humility. The saints, while making progress towards this perfection, came to humility- this is why we are always saying that the man who is getting closer to God looks on himself more and more as a sinner. Who are the children that the Law says must not fall from the roof top? These children are the thoughts generated in our souls, which must be guarded through humility lest they fall out of the house. So it is completed, it has its protecting walls, its roof of virtues; there it is, the house of perfection we are speaking of, complete with its crowning virtue of humility and all that it needs to complete it.

St. Dorotheos of Gaza