Daniel 1:10-13

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.”