Rashi on TanakhJonah 3

overturned Destroyed. [He did not say, “Destroyed,” because “overturned” has two meanings, bad and good. If they do not repent, it will be destroyed; if they repent, then “overturned” refers to the people of Nineveh, that they will be changed from bad to good, and they will repent. Gloss of Rabbi Akiva(?)]

his royal robe Heb. אַדַּרְתּוֹ, the cloak of his honor.

And he caused it to be proclaimed Heb. וַיַּזְעֵק, he commanded to proclaim

By the counsel of the king and his nobles—By the counsel of the king and his nobles, they commanded to announce.

and they shall call mightily to God—They bound the dams alone and the young alone. They said to Him, “Lord of the world! If You have no pity on us, we will not have pity on these.” [See Taanith 16a]

Whoever knows—the sins he has committed, shall repent.

and God will relent—He will think about the evil to repent of it.