The promises that the people of Judah had vowed to the Lord, the Lord is asking them to perform through his prophet Nahum, for the Lord was going to completely uproot the Assyrian’s who likely hindered the worshipping practices of the people of Judah. Merriam-Webster’s dictionary defines the word “vow” as a solemn promise, one by which a person is bound to an act, service or condition. It is synonymous to the words: pledge, oath and promise.

When we vow to the Lord, we must not be slack in keeping/performing it, for God does not have any pleasures in fools (Ecclesiastes 5:4). We find in Jephthah, the classic example of a man who hastily vowed to the Lord and that cost him his very own daughter (Judges 11:34).
Jesus said, let your ‘yes’ be ‘yes’ and your ‘no’ be ‘no’ for anything else that proceeds from your mouth is of the evil one (Matthew 5:37).

Points to ponder:
Don’t swear or make vows that you cannot be sure of fulfilling, but if you do or have done, “Perform thy vows” says the Lord, for there will be no one to hinder you. So when we vow to the Lord, let us be bound to the act of loving him with all our being, and to the service of reconciling man with God on the condition that we are God’s ambassadors. Let this be our pledge, our oath and our promise and let us perform it.

Nahum 1:15 (KJV)
15 Behold upon the mountains the feet of him that bringeth good tidings, that publisheth peace! O Judah, keep thy solemn feasts, perform thy vows: for the wicked shall no more pass through thee; he is utterly cut off.

Ecclesiastes 5:4 (KJV)
4 When thou vowest a vow unto God, defer not to pay it; for he hath no pleasure in fools: pay that which thou hast vowed.

Matthew 5:37 (KJV)
37 But let your communication be, Yea, yea; Nay, nay: for whatsoever is more than these cometh of evil.