One thing I have learned from having kids is never make a promise you are not sure you can keep. They remember to the four thousandth generation. The phrase I used in most cases where I was asked to play a game, hit some balls, or help with a project was and continues to be "We'll see."
It was devastating for both my children and I the first time I had to break an oath. To get home after going to a sport camp, a youth outing, or doing another project of my own and realize that I had spaced off what had been so important to them. There was no justifying it in their or my eyes. I had disappointed them, and it hurt us both.
I decided that if ever I was to make an oath to my children I would do WHATEVER it took to keep it no matter how it hurt or whatever it would cost. No amount of cost would ever hurt as much as the pain I caused my children.
In Psalm 15, David writes of the one "who may live on your holy mountain". Along with those "whose walk is blameless", "who speak the truth", "who does no wrong to a neighbor", and "fears the Lord" David adds this person-
"who keeps an oath even when it hurts, and does not change their mind;" --Psalm 15:4
I find it interesting that David puts oath-keeping on equal ground with loving your neighbor, fearing the Lord, and not slandering. We talk about those other three, but how are we with keeping an oath or promise?
Think of the oaths you have made in your life. Marriage vows, job contracts, even cell phone plans. We enter into these with fear and trembling at times, but at others we flippantly strike hands or sign on the line without thinking of the consequences of not being able to keep our word. Our thought is, (IF we think about it) "If it doesn't work out, I can just walk away." This does not work with God.
You see God is the covenant keeper. When He makes an oath, IT IS KEPT. That is why we can hold to the hope of salvation and that Christ will return. God's promises are ALWAYS kept. He expects no less from us. This is why David has it on this list of those "who may dwell in [the Lord's] sacred tent." When we keep our vows, no matter how big or small, it is another way we show ourselves to be like our Father in heaven.
Think of God's vow to Adam and Eve way back at the beginning. In Genesis 3:15 God promises that He will send one who would crush the head of the snake even as the snake struck his heel. This was the picture of the fulfillment of Jesus coming to die for our sins. Did it hurt to keep that promise? Most assuredly! But God kept it.
So, before you shake hands, say yes, or promise you'll do that thing, be sure you are ready to follow through no matter the cost.