Our Scripture reading today is Numbers 30:1-2.
Verse 2, "If a man vow a vow unto the LORD, or swear an oath to bind his soul with a bond; he shall not break his word, he shall do according to all that proceedeth out of his mouth."
Moses reminds the people of how important their word is.  They did not sign contracts like we do today.  Their word was just as binding as a signature is today.  When a vow was made an offering was given along with it and this became even more binding than one's word.  We might say that a vow was a promise made and it could not be broken.  
Our relationship with God and others is built on trust.  God can be fully trusted.  His record is spotless and it always will be.  He has given us promise after promise in His Word and they in time, will be fulfilled.  Titus 1:2, "In hope of eternal life, which God, that cannot lie, promised before the world began."  It is this level of trust that we should seek to provide in all of our relationships.  If we make a promise, we need to come through on whatever we promised. 
By God's grace we can build or re-build trust by being men and women of our word.