Who is there who speaks and it comes to pass, unless the Lord has commanded it? Is it not from the mouth of the Most High that both good and ill go forth?
The question we wish to first ask is, “To whom do the words ‘who is this’ apply?”
We should note that the Hebrew wording is, “Who is this.” It is spoken in a belittling, slightly sarcastic, or even taunting way against mere ‘speakers’.
Who are the possible candidates?
A. Good Angels. Whenever angels speak in Scripture, they utter the words given them by the direct command of God. They do not expostulate or offer opinions; nor do they ever speak a word from their own minds. Hence, their words unfailingly come to pass. Therefore, the passage cannot be referring to them.
B. Evil Angels. Whenever demons (or Satan) speak in Scripture, they utter lies (John 8:44). Thus their words do NOT come to pass. Even Satan’s prediction regarding Job turned out wrong. If you remember the story of Job, you’ll recall that Satan predicted that Job would turn from God if he lost his temporal goods. Satan certainly can’t speak and have it come to pass. Any sensible gambling man would’ve put money on Job turning from God. Satan can neither predict the future nor affect the outcome of events. All things are ordained by God.
C. Men. The only men who have ever spoken with absolute certainty that their words would come to pass were the prophets and Apostles when they spoke under the inspiration of the Holy Spirit, and, like the angels, spoke only the words commanded by God.
This is a warning against presumptuous speech.
What about oaths, promises, vows and covenants?
Oaths are expressly forbidden by Christ. (Mat. 5: 34, 36; 23:16, 18, 20-22). They involve a certainty, indeed, a sovereignty, over the future that no creature can possess. James 4:13-16 even forbids self-confident speaking regarding the future.
Promises are different in principle from oaths. They contain allowance (though unspoken, perhaps) for unforeseeable events thwarting the fulfillment.
Vows are a special, religious kind of self-imposed promise. They bind the individual into a fulfillment of certain acts within a time period specified by the maker of the vow. Once the vow is fulfilled, the individual is released. Numbers 6:2-21
Covenants are like vows, with the exception that they are two-way and not one-way. A covenant binds two parties into an agreement which is valid so long as both parties live. Breaking the covenant does not release one from its power. It is only terminated at the death of one party (Rom. 7:1-3).