It did not have authority to eat Jonah

[Mary Naeem]

Pope Shenouda III

It did not have authority to eat Jonah nor to secrete digestive enzymes onto him to absorb him. No, but rather it swallowed him in order to take him into its inner bosom and keep him safe there until he would approach his destination. The whale was a free means of transport by which Jonah reached the nearest point to his embarkation stop.
It was as though Jonah was in a protected submarine sailing underwater. That great fish was sent to rescue him from the sea and its tumults. It was like tribulations, appearing fearful from the outside whilst entailing within them all benefit. Jonah was inside the fish for three days, sound and not conquered by the whale, just as Christ was in the tomb for three days and was not conquered by death.