“But Daniel made up his mind that he would not defile himself with the king’s choice food or with the wine which he drank; so he sought permission from the commander of the officials that he might not defile himself.”
Daniel made up his mind that he would not eat from the king’s food because it was, most likely, from sacrifices. It was an unclean food. Daniel did not want to “defile” himself by partaking of it. We can apply this to our lives in which we should not do anything which could cause spiritual harm to ourselves; such as exposing ourselves to worldly values and thoughts.