the bible says

your word is a lamp to my feet and a light for my path
psalm 119:105 niv

all scripture is God-breathed and is useful for teaching, rebuking, correcting and training in righteousness
2 timothy 3:16 niv

for the word of God is living and active. sharper than any double-edged sword, it penetrates even to diving soul and spirit, joints and marrow; it judges the thoughts and attitudes of the heart
hebrews 4:12 niv

Jesus answered, "it is written: 'man does not live on bread alone, but on every word that comes from the mouth of God'"
matthew 4:4 niv