Imitation of Christ

Habitus et tonsura modicum faciunt, sed mutatio morum et integra mortificatio passionem verum faciunt religiosum. Qui aliud quærit, quam pure Deum, et animæ suæ salutem, non inveniet nisi tribulationem et dolorem. Non potest etiam diu stare pacificus, qui non nititur esse minimus, et omnibus subjectus. Ad serviendum venisti, non ad regendum, ad paciendum et laborandum scias te vocatum, non ad otiandum, vel fabulandum. Hic ergo probantur homines sicut aurum in fornace. Hic nemo potest stare nisi ex toto corde si voluerit propter Deum humiliare. 
 

The clothing and outward appearance are of small account; it is change of character and entire mortification of passions which make a truly religious man. He who seeks anything save God

and the health of his soul, shall find only tribulation and sorrow. Nor can he stand long in peace, who does not strive to be least of all and servant of all. You are called to endure and to labour, not to a life of ease and trifling talk. Here therefore are men tried as gold in the furnace. No man can stand, unless with all his heart he will humble himself for God's sake.

Imitation of Christ, I, 17:2