. . . “Be careful to obey all the law my servant Moses gave you; do not turn from it to the right or to the left, that you may be successful wherever you go. Keep this Book of the Law always on your lips; meditate on it day and night, so that you may be careful to do everything written in it. Then you will be prosperous and successful.
— Joshua 1:7-8 NIV
The reason for this is that when one meditates on the Word one begins to see reality from God’s perspective; one begins to see reality for what it actually is. Those who meditate on the Word become wise. David said that by meditating on God’s Word he became wiser than his enemies, teachers, and elders (Psalm 119:97-100). The wise person knows what to do and how to prosper and be successful in life. That’s why Solomon prayed for wisdom when he wanted success as King of Israel (I Kings 3).
Meditation on the Word of God is the practice of focusing one’s thoughts on the Word to reflect on it, ponder over it, memorize it, and pray about it. It helps us with what the Apostle Paul would call the “renewing of our minds” and thus keeps us from being “conformed to this world” (Romans 12:2). It should not be confused with Eastern mystical meditation. Mysticism usually involves the emptying of the mind, whereas Christian meditation involves filling the mind with the Word of God.
Don’t forget the obedience part of God’s admonition to Joshua. It doesn’t make much sense to meditate on the Word and never put it into practice. Wise people don’t just know things, they also do things.