Daniel 1:10

And the prince of the eunuchs said unto Daniel, I fear my lord the king, who hat appointed your meat and your drink; for why should he see your faces worse liking than the children which are of your sort? then shall ye make me endanger my head to the king. - Daniel 1:10

The Prince of the eunuch had the special job of making sure that the eunuchs were taken care of. After a three year tutorage, they would appear before the king and he would test them. If the prince of the eunuchs had the appearance of not doing his job then the king would most likely take his life.

This is one example of "Fearing a King"