The word of God gives life. Notice in Proverbs 4:22 the scripture says the word of God is life. And that life will drive any and all death out of your body. Notice, in Romans 4:19 it says that Abraham considered not the deadness of his body nor the deadness of Sarahs womb. Notice, they both had a condition in their flesh that the scripture calls death. All forms of death is simply the absence of life. Your flesh has no life in itself. The only life in your flesh is the life your spirit feeds into it. In Proverbs 14:30 it says, "A sound heart(spirit) is the life of the flesh." In Proverbs 4:20-21 it says to keep the word in your eyes, ears, and mouth and by that you keep the word in the midst of your heart.
You keep the word in your heart for the life of the word to be feed to your flesh constantly. Abraham means-father of a multitude. Sarah means-princess of the multitude. Everytime they heard their name called they were hearing the word. Everytime they said their name they were hearing the word. Everytime they saw their name written they were seeing the word. All the while that life is being feed into their spirit. You see the first thing the word has to do is get your mind and spirit in agreement with it. 1Thessalonians says you are spirit, soul, and body. The life you feed your spirit has to come through your soul to get to your flesh.
If you contine to feed your spirit the word of God it will run death out. Abrahan and Sarah ran that death out of their bodies with the word of God. It's just like you have a glass full of muddy water, if you continue to pour in some nice clear spring water at some point you will have a glass full of clear spring water. If you continue to feed your flesh the life of the word you will have a body full of life. And that life is the life of God for God and the word are one (John 1:1).