"All scripture is given by inspiration of God, and is profitable for doctrine, for reproof, for correction, for instruction in righteousness: That the man of God may be perfect, thoroughly furnished unto all good works." (vv16,17)
These two verses studied on their own are a testimony to the power of the Word. When we study His Word we become more complete (perfect) and we are empowered to live a holy life (Thy word have I hid in mine heart, that I might not sin against thee.- Psalm 119:11).
Notice how complete scripture is. The Word illuminates what is true (doctrine), what is false (reproof), what we should not do (correction), and what we should do (instruction in righteousness). It is the perfect model for teaching.
Now, consider the context. Paul has assured Timothy to stand firm on the foundation of faith that is already in his life. He has warned that "perilous times shall come." And, then points him back to the complete and perfect Word of the Lord. Men we have all that we need to withstand the enemy: to stand faithful with our minds set on our purpose. Let's continue in the Word.