Daniel 1:8-17 NIV
But Daniel resolved not to defile himself with the royal food and wine, and he asked the chief official for permission not to defile himself this way. Now God had caused the official to show favor and compassion to Daniel, but the official told Daniel, “I am afraid of my lord the king, who has assigned your food and drink. Why should he see you looking worse than the other young men your age? The king would then have my head because of you.” Daniel then said to the guard whom the chief official had appointed over Daniel, Hananiah, Mishael and Azariah, “Please test your servants for ten days: Give us nothing but vegetables to eat and water to drink. Then compare our appearance with that of the young men who eat the royal food, and treat your servants in accordance with what you see.” So he agreed to this and tested them for ten days. At the end of the ten days they looked healthier and better nourished than any of the young men who ate the royal food. So the guard took away their choice food and the wine they were to drink and gave them vegetables instead. To these four young men God gave knowledge and understanding of all kinds of literature and learning. And Daniel could understand visions and dreams of all kinds.