Scholars of the Children of Israel who became Muslims especially applied it to stories about the Bull and the Fish they had seen in the former scriptures, altering it to mean something strange. For now I shall explain three ‘principles’ and three ‘aspects’ in connection with your question.

FIRST PRINCIPLE

When some of the Israelite scholars became Muslims, their former knowledge became  Muslim along with them and was ascribed to Islam. However, what they knew contained errors which were certainly their errors and not Islam’s.

SECOND PRINCIPLE

On comparisons and metaphors passing from the elite to the common people, that is, on their falling from the hands of learning to those of ignorance, with the passage of time they are imagined to be literally true. For example, when I was a child an eclipse of the moon  occurred. I asked my mother: “Why has the moon gone like that?” She replied: “A snake  has swallowed it.” “It can still be seen,” I said. She replied: “The snakes up there are like glass; they show the things inside them!”

For a long time I recalled this childhood memory. Pondering over it, I would say:

“How could such a false superstition come to be repeated by serious people like my mother?” Then when I studied astronomy I realized that people like her who repeated it supposed a metaphor to be reality. For when the vast circle called the zodiac, which is the circle denoting the degrees of the sun, and the circle of the declination of the moon, which is the circle depicting its mansions, pass over one another, it gives each of the two circles the form of an arc. Using a subtle metaphor the astronomers called the two arcs “the two great serpents.” They called the points of intersection of the two circles “the head” and “the tail.” When the moon comes to the head and the sun to the tail, in the terminology of astronomy, an interposition of the earth occurs. That is, the globe of the earth passes right between the two of them and the  moon is eclipsed. According to the above metaphor, “the moon has entered the serpent’s mouth.” Thus, when this  elevated  and  scholarly metaphor  entered  the  language  of the  common people, in the course of time it took on the shape of a huge snake swallowing the moon.

Thus,  with a  sacred  and  subtle metaphor  and  meaningful allusion,  two  great angels were called the Bull (T. Sevr; Ar. Thawr) and the Fish (T. Hût; A. Hut), but on entering the common language from the elevated tongue of the prophethood, the metaphor was transformed  and  given  a  literal  meaning,  and  they took  on  the  form  of  a  truly enormous bull and awesome fish.