Tertullian

The exception of certain kinds from use as food is a partial fast.… Daniel and his companions, preferring as they did a diet of vegetables and the beverage of water to the royal dishes and decanters, were found "more handsome" … and in addition were more spiritually cultured. For God gave to the young men knowledge and understanding in every kind of literature, and to Daniel in every word, and in dreams and in every kind of wisdom; which [wisdom] was to make him wise in this very thing also, namely, by what means the recognition of mysteries was to be obtained from God.