Suppose we make a promise that seems fully reasonable. Though later, circumstances arise in which we have to neglect someone in need in order to fulfill that promise.
Maybe a person came to visit and was just leaving in time to fulfill the original promise, but they slip and fall; being injured and in need of medical attention. Do we leave the injured person unattended because we made a promise? Of course not.
But, what if we are not doing what God called us to, because we are busy keeping our word elsewhere, and miss the opportunity to meet a spiritual need. Isn't that the same thing? The only difference is where the wound is located.
Maybe we gave our word and later realized God was not calling us to it. Do we ignore what God is calling us to in order to meet the previous obligation? Does He come first or second?
In such cases, we have a choice. Is our word God? Is the law our God? Is what people think our God? Or, does God's will for us come above all gods?
If we make a promise, only later to realize our error ... in order for God to be first, we just might have to eat humble pie. But, therein is a lesson to be learned. The error in making such a promise was not God's.
There is an easy way to not make the same mistake twice. Do not make promises you may not be able to keep. We can say, 'if the Lord be willing;' James 4:15. But, that is about all we can honestly agree to, knowing that none of us knows what tomorrow may bring.
Perhaps what God is calling us to, today, may not be the same as tomorrow. All any of us can rightly do is what God is calling us to, until God calls us to move on.
The scribe said, Well, Master, thou hast said the truth: for there is one God; and there is none other but he: And to love him with all the heart, and with all the understanding, and with all the soul, and with all the strength, and to love his neighbour as himself, is more than all whole burnt offerings and sacrifices.
And when Jesus saw that he answered discreetly, he said unto him, Thou art not far from the kingdom of God. Mark 12:32-34
Only once we've heard from God can we be 'A Man of HIS Word'.
And to walk with Him, we must first be available.