(I Samuel 1:11) - "And she vowed a vow, and said, O Lord of hosts, if Thou wilt indeed look on the affliction of Thine handmaid, and remember me, and not forget Thine handmaid, but wilt give unto Thine handmaid a man child, then I will give him unto the Lord all the days of his life, and there shall no razor come upon his head."
Hannah's inability to have a child was directly linked to the fact that God was working in her life and was preparing her for the future. Hannah was grieved in her heart due to her barrenness, not knowing that all the while God had a special plan for her life and her future.
It was due to Hannah's barrenness that caused her to really get serious enough concerning her desire to have a child that she, through her desperation, make a promise to God. Hannah promised God that if He would allow her to have a "man child", she would give him back to the Lord for His service. Hannah was not playing "Let's Make A Deal" with God, but was showing her devotion to Him by her willingness to dedicate her son to the work of the Lord.
Promises that you and I make are very important to the person or persons we make them to, but the promises we make to God are even more important. If you read the rest of Hannah's life story, you will find that she kept her promise to God by giving Samuel back to Him.
God is also a promise keeper. In fact there is not one promise that He has made that He has not kept.
If you have made promises to God, I pray that you have not gone back on your word. One of the ways we can be faithful to God is to be faithful to keep and to fulfill the promises we have made to Him.