How Serious is a Vow? January 31st A.M Service

How Serious is a vow? 1 Samuel 1:9-20 So Hannah rose up after they had eaten in Shiloh, and after they had drunk. Now Eli the priest sat upon a seat by a post of the temple of the Lord .  And she was in bitterness of soul, and prayed unto the Lord , and wept sore. ...