The Word of God is important to us as Christians for three reasons. 1) It provides light and comfort. 2) It is a sanctifying agent. 3) It is a weapon to be used to advance the Kingdom of God, fight off temptation and cast down everything that exalts itself against the knowledge of God.
Use of the term light when referring to the Word of God means direction. (Psalm 119:105) The Holy Spirit speaks to us through the written Word of God. This is how we obtain wisdom and direction. This is what happens when we fellowship with the Lord by meditating on His word.
The Scriptures also admonish us to walk in the light that we are given. (1 John 1:5-10) This means we are to live by the wisdom and direction the Holy Spirit gives us. The Holy Spirit knows every situation we face in life. He can and will reveal to us the nature of any situation we face and instruct us how to handle it. When we govern ourselves accordingly, we walk in the light. Walking in the light produces fellowship with other Christians.
As Christians, we are to believe in the Word of God as it is delivered to us by the Holy Spirit. Then we will have spiritual understanding and God can use us to bless others. This is having the light of life. (John 8:12)
The Word of God is our comfort in affliction. (Psalm 19:49-50) Jesus told his disciples, "In this world you will have tribulation". John 16:33 The world is a source of tribulation, but Jesus, the Word of God (John 1:1), has overcome the world. That means He has overcome tribulation. Therefore, we Christians can also overcome tribulation through the Word of God.
Tribulation is a time for exercising patience. (Romans 12:12) Patience produces character. Character produces hope -- expectation of deliverance. (Romans 5:3-5) Exercising patience in tribulation demonstrates our love for God. It is also a means of avoiding further disaster. (James 1:4)
The Word of God teaches us the righteous have many afflictions. However, God delivers us from all of those afflictions. (Psalm 34:19) This is our comfort and our hope.
The Word of God sanctifies us. The word sanctify comes from the Greek word hagiazo. It means to "withdraw from fellowship with the world by first gaining felowship with God". Individuals are first sanctified by the Word of God when they are born again. This is because they become born again by believing the word that was preached to them. (Mark 16:16) Becoming born again separates individuals from the world because they are now new creations in Christ Jesus. (2 Corinthians 5:17) After being born again, Christians are set apart (sanctified) for Christian service by the word of God. (John 15:3-5; 127:17; 1 Corinthians 1:2; 6:11; Ephesians 2:10; Colossians 1:16-18)
The Word of God is a weapon to be used to advance the Kingdom of God. This is because it pierces. It penetrates the heart of hearers. It discerns the thoughts and intents of men's hearts. No creature is hidden from the Holy Spirit's sight. He knows what is needed to win persons to Jesus Christ. He also knows what is needed for spiritual growth and edification of Christians. (Hebrews 4:12,13) Therefore, it is vitally important that the Word of God be preached under the anointing of the Holy Ghost.
The Word of God is also a weapon to be used to fight off temptation. While in the wilderness, Jesus responded to every instance of temptation by saying, "It is written..." Luke 4:1-12. Studying the Word of God helps us fight off temptation just as Jesus did.
Studying the Word of God also helps us keep our thoughts and ideas in line with God. Apostle Paul states imaginations and every high thing that exalts itself against the knowledge of God should be cast down. (2 Corinthians 10:5,6) This includes our own thoughts (Isaiah 55:6-9) as well as heresies that plague the Body of Christ. (Galatians 2:11; Titus 1:11,12)
Therefore, as a source of light and comfort, a sanctifying agent and a weapon, the Word of God is vitally important to our Christian life.