The Bible, God’s Word, is spiritual food. God uses His Word to equip His people to do His will.
Deuteronomy 8:3 (NKJV) So He humbled you, allowed you to hunger, and fed you with manna which you did not know nor did your fathers know, that He might make you know that man shall not live by bread alone; but man lives by every word that proceeds from the mouth of the Lord. (Jesus quotes this verse in Matthew 4:4)
2 Timothy 3:16-17 (ESV) All Scripture is breathed out by God and profitable for teaching, for reproof, for correction, and for training in righteousness,that the man of God may be complete, equipped for every good work.