David's father sent him on a mission to deliver supplies to his brother and the Israelite army. David delivered the supplies, and having done his duty, could have quickly left and returned to work caring for his father's sheep. No one expected him to fight Goliath. His elder brother even scolded him for the idea.
How could a shepherd boy with a slingshot and a few stones defeat this huge warrior? From a human perspective it was impossible. But David knew Goliath was wrong in defying the God of the armies of Israel. He stood up for what was right at the risk of his life. He had the courage to face the giant because he knew his God was greater.
It is easy to go about our daily tasks, avoiding confrontations, just doing our duty and trying to stay out of trouble. It is good to live a peaceful life. But it is wrong to shut our eyes to evil and injustice. We must stand against wickedness.
Raoul Wallenberg was a citizen of neutral Sweden during World War II. He didn't need to fight; he could have stayed at home and read about the results of the war in the newspaper. But no, he heard that thousands of innocent Jews were being murdered in Hungary by the Nazis, and he tried to rescue as many as he could. It may have seemed like a hopeless task; he couldn't rescue everyone. All the forces of evil were working against him. His life was in danger.
Still he persevered, saving tens of thousands of lives. In the end, he was arrested by Soviet "Allies" and after rescuing so many Jews, died alone in a Soviet prison with no one to rescue him. Even today his fate remains shrouded in mystery. He could have lived out his days unknown in quiet peace, but he chose instead to fight against evil. He faced the giants. He made a difference in this world.
If we do not fight for what is right, who will? The Bible says, "When the enemy comes in like a flood, the Spirit of the Lord will raise up a standard against him." Stand against injustice. Your actions, great or small, can make a difference in this world. God is bigger than the greatest giants we will ever face.
"If God be for us, who can be against us?" --Romans 8:31