There are two senses in which the precepts in the Bible give life:
First, they enliven ("quicken" as the KJV puts it) our spiritual life as believers. Have you ever met a vibrant, wide-awake Christian who does not spend much time in the Bible? We require food for our natural bodies, and we require the milk and meat of the Word for our spiritual bodies. Without a steady diet of it, we will wither and waste away to nothing as Christians.
Deuteronomy 8:3 Man shall not live by bread alone; but man lives by every word that proceeds from the mouth of the LORD. (Jesus also quotes this verse when He is tempted by the devil.)
Psalm 119:50 This is my comfort in my affliction, For Your word has given me life.
The word of God is called life in many places throughout scripture. In John 6:63, Jesus says "The words that I speak to you are spirit, and they are life", and Paul exhorts believers, in Philippians 2:16, to "hold fast the word of life".
These words are so important, yet people often pay little attention to them. If they do go to church and hear a sermon, many are not even listening, let alone applying the truth they hear to their lives. Never take the opportunity to hear good preaching for granted. As long as it is God's word being preached, there is always something new to learn, no matter how well you know the Bible. Eating food will do your body no good if you do not digest it to extract the nutrients, and hearing the Word will do no good unless you think about it and apply it.
Since this Book is the word of life, we certainly ought to consume it more often than once a week, or even three times a week! (If you go to church on Sunday night and Wednesday night.) At the very least, let us read a little bit every day. I'm very bad about asking people what they're learning in the Bible—it always comes out awkward and unnatural—but we should be keeping each other accountable. I am amazingly blessed to be able to devote so much time to reading and meditating right now, and I am trying to soak it up in every way possible, since it is likely I will soon be in a much busier stage of life, and wise counselors have encouraged me to collect a store of scripture to draw on ahead of time.
However there is a second way in which the Word gives life: even before it started its job of keeping us alive as Christians, God used it to bring us to life when we were dead in sin. This is even more astonishing that the word's work nourishing us when we are already believers. No matter how much food you feed to a dead man, nothing will happen—the life-giving power of physical food only works while there is a spark of life to be sustained. In contrast, the Bible is the conduit for God's almighty power: power that not only sustains life, but even raises from the dead.
Romans 10:17 So then faith comes by hearing, and hearing by the word of God.
John 5:24 Most assuredly I say to you, he who hears My word and believes in Him who sent Me has everlasting life and shall not come into judgment, but has passed from death into life.
This is why it is so important to use scripture when witnessing to people. No arguments, logic, or life experience will convince them without the life-giving words of God.
We need not fear to address gospel precepts to dead sinners, since by them the Spirit gives them life. —Charles H. Spurgeon