This is addressed to the so-called "Torah Observant" Christians, the modern Judaizers : why, if we're to serve by Torah, did Jesus say that you are doing a work of the evil one if you do as the Torah permitted and make a vow?
Matthew 5
33“Again, you have heard that [z]the ancients were told, ‘[aa]YOU SHALL NOT [ab]MAKE FALSE VOWS, BUT SHALL FULFILL YOUR [ac]VOWS TO THE LORD.’ 34But I say to you, take no oath at all, neither by heaven, for it is the throne of God, 35nor by the earth, for it is the footstool of His feet, nor [ad]by Jerusalem, for it is THE CITY OF THE GREAT KING. 36Nor shall you take an oath by your head, for you cannot make a single hair white or black. 37But make sure your statement is, ‘[ae]Yes, yes’ or ‘No, no’; anything beyond these is [af]of the evil one.
James 5
12But above all, my brothers, do not swear, either by heaven or by earth or by any other oath, but let your “yes” be yes and your “no” be no, so that you may not fall under condemnation.
So, James verifies we got the right message.
Matthew 5
33“Again, you have heard that [z]the ancients were told, ‘[aa]YOU SHALL NOT [ab]MAKE FALSE VOWS, BUT SHALL FULFILL YOUR [ac]VOWS TO THE LORD.’ 34But I say to you, take no oath at all, neither by heaven, for it is the throne of God, 35nor by the earth, for it is the footstool of His feet, nor [ad]by Jerusalem, for it is THE CITY OF THE GREAT KING. 36Nor shall you take an oath by your head, for you cannot make a single hair white or black. 37But make sure your statement is, ‘[ae]Yes, yes’ or ‘No, no’; anything beyond these is [af]of the evil one.
James 5
12But above all, my brothers, do not swear, either by heaven or by earth or by any other oath, but let your “yes” be yes and your “no” be no, so that you may not fall under condemnation.
So, James verifies we got the right message.