As soon as a man comes of age, if he be a freeman he is in his own power in all matters concerning his person, for instance with regard to binding himself by vow to enter religion, or with regard to contracting marriage.
 Thomas Aquinas, Summa Theologica (1274). copy citation

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Author Thomas Aquinas
Source Summa Theologica
Topic marriage religion
Date 1274
Language English
Reference
Note Translated by Fathers of the English Dominican Province
Weblink http://www.gutenberg.org/cache/epub/18755/pg18755-images.html

Context

“Hence the conditions necessary for a vow are not altogether ensured, when a man who is under another's power vows that which is in that other's power, except under the condition that he whose power it concerns does not gainsay it. Reply Obj. 2: As soon as a man comes of age, if he be a freeman he is in his own power in all matters concerning his person, for instance with regard to binding himself by vow to enter religion, or with regard to contracting marriage. But he is not in his own power as regards the arrangements of the household, so that in these matters he cannot vow anything that shall be valid without the consent of his father. A slave, through being in his master's power, even as regards his personal deeds, cannot bind himself by vow to enter religion, since this would withdraw him from his master's service.” source