Thomas Aquinas

If a servant is faithful to you, let him be to you as your own soul, etc. Ecclesiasticus 33:31. The wise man shows three things concerning master and servant, namely, what is required on the part of the servant; likewise, what the disposition of the master toward the servant ought to be; likewise, what the use of the servant ought to be. On the part of the servant, faithfulness is required, in which lies the good of the servant, because he ought to give both what he is and all that is his to his master. Matthew 24:45: a faithful and prudent servant, etc. And he says if he is faithful, because faithfulness is found among few. Proverbs 20:6: a faithful man, who shall find? Such a servant, then, ought to be held by his master as a friend in affection. Hence he says let him be to you as your own soul. For this is proper to friends, that their soul be one in willing and not willing. Acts 4:32: of the multitude of believers there was one heart and one soul. In which it is given to be understood that there is a certain agreement between master and servant, because the faithful servant passes over into a friend. The use of him is that he be treated as a brother; for he is a brother, both as to the generation of nature, because by the same author. Job 31:13: if I have despised to submit to judgment with my servant. Malachi 2:10: is there not one father of us all? Is there not one God? And as to the generation of grace, which is the same. Galatians 3:27f.: for as many of you as have been baptized in Christ have put on Christ; there is neither Jew nor Greek, there is neither servant nor free, there is neither male nor female, for you are all one in Christ Jesus. Matthew 23:8: you are all brothers. These words, moreover, suit the matter of this epistle. For just as above he showed how spiritual prelates ought to conduct themselves toward their subjects, so here how temporal masters toward temporal servants, and how a faithful servant stands toward his master.