Jonah 2:1

a huge fish—It was a male, and he stood there with room, so that he did not think to pray. The Holy One, blessed he He, hinted to the fish, and it spewed him out into the mouth of a female, which was full of embryos, and it was crowded there, and he prayed there, as it is said: (verse 2) “from the belly of the fish (הַדָּגָה).” [from Pirké d’Rabbi Eliezer ch. 10, according to Yalkut Shimoni ; Midrash Yonah, second version, Otzar Medrashim p.219] [And the Lord appointed—Those sixteen days that Israel was missing the manna, since they did not eat it for a complete forty years - God took this manna and sustained the fish so that Jonah would not be digested in its intestines, and Jonah, too, ate within it from this manna. Therefore, it is stated וַיְמַן, the letters מָן י"ו sixteen [days of] manna. Similarly, וַיְמַן קיקָיוֹן, and He appointed a kikayon, for he ate four omers; therefore, it says four times וַיְמַן (4:6 ff.). And in Greek, manna is called “kika.” For that reason, it is stated: קִיק יָוָן ; i.e, manna in Greek. -[Sod Mesharim]

And the LORD invited a great fish to swallow Jonah, and Jonah was in the fish’s guts for three days and three nights.

and Jonah remained: no one can survive in the belly of a fish even for an hour, so if this is the duration, it must have been a miracle.

The LORD appointed: ...at the moment that Jonah was cast into the sea, God appointed the fish that swallowed him, so that he did not drown. And this was one of the miracles. In Pirkei de Rabbi Eliezer, Rabbi Tarfon said that the fish was appointed from the six days of creation to swallow Jonah.