§ 6. The Sermon on the Mount (According to Matthew)

Numbers 30 provides an example of the kind of teaching Jesus is talking about. Even here it is plain that a person is not required to enter into a vow in the first place, but if he does, he must fulfill it:

Numbers 30:1–2

Moses spoke to the heads of the tribes of the people of Israel, saying, "This is what the LORD has commanded. If a man vows a vow to the LORD, or swears an oath to bind himself by a pledge, he shall not break his word. He shall do according to all that proceeds out of his mouth."

We Literally Cannot Swear

The most fundamental principle of this teaching is that we as created beings do not possess within ourselves the power to cause things to happen in this world. If our own words prove untrue—whether we lied or were simply mistaken—we are in fact powerless to change the things by which we have sworn. We cannot even guarantee that we will live another day!

James 4:15
Instead you ought to say, "If the Lord wills, we will live and do this or that."

It might be helpful to contrast an oath with collateral.

Collateral is given as a promise to pay a loan; if we do not pay the loan then the thing offered in collateral becomes the property of the lender. But the collateral thing itself does not change in nature or character—only its ownership changes.

On the other hand, an oath gives the thing sworn by as proof: it is something we know certainly, and the oath asserts that what we are saying is just as certain.

If we were to swear by heaven and then what we said were to fail, would heaven therefore fail? Never!

This is how we know we do not possess the ability to swear.

Now, the reason we do not possess the ability to swear is that oaths are generally made by something higher or greater than ourselves. We can compare the oath God took when He made Abraham a promise:

Hebrews 6:13–14, 16–18
When God made a promise to Abraham, since he had no one greater by whom to swear, he swore by himself, saying, "Surely I will bless you and multiply you…."
For people swear by something greater than themselves, and in all their disputes an oath is final for confirmation. So when God desired to show more convincingly to the heirs of the promise the unchangeable character of his purpose, he guaranteed it with an oath, so that by two unchangeable things, in which it is impossible for God to lie, we who have fled for refuge might have strong encouragement to hold fast to the hope set before us.

The "two unchangeable things" of Hebrews 6:18 above are:

1. God said, "I will" (and "it is impossible for God to lie"), and
2. God confirmed it with the oath by Himself (and it is impossible for God to change).

In contrast to God, we the created are quite capable of lying and of changing our aims and hearts.

The Law Warns Against Swearing

The reasons Jesus gives for not entering into a vow are also consistent with the teaching of the Law, which always warned against making vows, too.

Deuteronomy 23:21–23
"If you make a vow to the LORD your God, you shall not delay fulfilling it, for the LORD your God will surely require it of you, and you will be guilty of sin. But if you refrain from vowing, you will not be guilty of sin. You shall be careful to do what has passed your lips, for you have voluntarily vowed to the LORD your God what you have promised with your mouth."

Ecclesiastes 5:1–2, 4–6
Guard your steps when you go to the house of God. To draw near to listen is better than to offer the sacrifice of fools, for they do not know that they are doing evil. Be not rash with your mouth, nor let your heart be hasty to utter a word before God, for God is in heaven and you are on earth. Therefore let your words be few.…
When you vow a vow to God, do not delay paying it, for he has no pleasure in fools. Pay what you vow. It is better that you should not vow than that you should vow and not pay. Let not your mouth lead you into sin, and do not say before the messenger that it was a mistake. Why should God be angry at your voice and destroy the work of your hands?

Heaven does not belong to us, nor is it within our sphere of influence, but rather it belongs to God and is where He reigns from.

Matthew 23:22

[Jesus said,] "Whoever swears by heaven swears by the throne of God and by him who sits upon it."

Isaiah 66:1-2

Thus says the LORD:
"Heaven is my throne,
and the earth is my footstool;
what is the house that you would build for me,
and what is the place of my rest?
All these things my hand has made,
and so all these things came to be,"
declares the LORD.

"But this is the one to whom I will look:
he who is humble and contrite in spirit
and trembles at my word."

See Isaiah 66:1-2 above.

Jesus here refers to Psalm 48, which makes clear the grandeur of God's chosen city—a grandeur that far exceeds anything we can do ourselves.

Psalm 48:1–3

Great is the LORD and greatly to be praised
in the city of our God!
His holy mountain, beautiful in elevation,
is the joy of all the earth,
Mount Zion, in the far north,
the city of the great King.
Within her citadels God
has made himself known as a fortress.

While we are to have self-control and conduct ourselves honorably, we still do not have the ability to change even the simplest of our physical characteristics. Rather, our characteristics tend to change over a lifetime—not at a whim:

Proverbs 16:31

Gray hair is a crown of glory;
it is gained in a righteous life.

Proverbs 20:29

The glory of young men is their strength,
but the splendor of old men is their gray hair.

The children of God have no real use for oaths because we are already required by God to be completely honest. James speaks of the condemnation that awaits the dishonest:

James 5:12

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.

In addition, we are concerned about pleasing Him not just with our words but with our hearts:

Ecclesiastes 12:14

For God will bring every deed into judgment, with every secret thing, whether good or evil.

The requirement and authority of God also far outweighs whatever a human institution might bring against us:

1 Corinthians 4:3-4

With me it is a very small thing that I should be judged by you or by any human court. In fact, I do not even judge myself. For I am not aware of anything against myself, but I am not thereby acquitted. It is the Lord who judges me.

Everything we say we will do is binding. We must speak truthfully about everything with everyone everywhere.

2 Corinthians 1:16–20, 23

I wanted to visit you on my way to Macedonia, and to come back to you from Macedonia and have you send me on my way to Judea. Was I vacillating when I wanted to do this? Do I make my plans according to the flesh, ready to say "Yes, yes" and "No, no" at the same time? As surely as God is faithful, our word to you has not been Yes and No. For the Son of God, Jesus Christ, whom we proclaimed among you, Silvanus and Timothy and I, was not Yes and No, but in him it is always Yes. For all the promises of God find their Yes in him. That is why it is through him that we utter our Amen to God for his glory.
But I call God to witness against me—it was to spare you that I refrained from coming again to Corinth.