Confession of Faith
Chapter 22: Of Lawful Oaths and Vows
Whosoever taketh an oath ought duly to consider the weightiness of so solemn an act, and therein to avouch nothing but what he is fully persuaded is the truth:1 neither may any man bind himself by oath to anything but what is good and just, and what he believeth so to be, and what he is able and resolved to perform.2
“You shall not take the name of the Lord your God in vain, for the Lord will not hold him guiltless who takes his name in vain.
and if you swear, ‘As the Lord lives,’
in truth, in justice, and in righteousness,
then nations shall bless themselves in him,
and in him shall they glory.” (ESV)
And Abraham said to his servant, the oldest of his household, who had charge of all that he had, “Put your hand under my thigh, that I may make you swear by the Lord, the God of heaven and God of the earth, that you will not take a wife for my son from the daughters of the Canaanites, among whom I dwell,
The servant said to him, “Perhaps the woman may not be willing to follow me to this land. Must I then take your son back to the land from which you came?” Abraham said to him, “See to it that you do not take my son back there.
But if the woman is not willing to follow you, then you will be free from this oath of mine; only you must not take my son back there.” So the servant put his hand under the thigh of Abraham his master and swore to him concerning this matter. (ESV)