What is shown in Nineveh seems similar to what is shown in Jeremiah when he says,
Jeremiah 18:7 At what instant I shall speak concerning a nation, and concerning a kingdom, to pluck up, and to pull down, and to destroy it;
Jeremiah 18:8 If that nation, against whom I have pronounced, turn from their evil, I will repent of the evil that I thought to do unto them.
And so we see after Jonah flees the first commission of the word of the LORD it says,
Jonah 3:1 And the word of the LORD came unto Jonah the second time, saying,
Jonah 3:2 Arise, go unto Nineveh, that great city, and preach unto it the preaching that I bid thee.
Jonah 3:4 And Jonah began to enter into the city a day's journey, and he cried, and said,
Yet forty days, and Nineveh shall be overthrown. (Jeremiah 18:7-8)
It does say God spake in times past in divers manners by the prophets (Heb 1:1) And when they were warned by Jonas the Prophet it says,
Jonah 3:5 So the people of Nineveh believed God, and proclaimed a fast, and put on sackcloth, from the greatest of them even to the least of them.
Jonah 3:10 And God saw their works, that they turned from their evil way;
And God repented of the evil, that he had said that he would do unto them; and he did it not.
Which is also in accord with Jeremiah 18:7-8
Jeremiah 18:8 If that nation, against whom I have pronounced, turn from their evil,
I will repent of the evil that I thought to do unto them.
And so we see again,
Jonah 3:10 And God saw their works, that they turned from their evil way;
And God repented of the evil...
As the LORD hath said, I have no pleasure in the death of the wicked; but that the wicked turn from his way and live
Similarly it says,
Ezekiel 33:7 So thou, O son of man, I have set thee a watchman unto the house of Israel; therefore thou shalt hear the word at my mouth, and warn them from me.
Mat 12:38 Then certain of the scribes and of the Pharisees answered, saying, Master, we would see a sign from thee.
Mat 12:39 But he answered and said unto them, An evil and adulterous generation seeketh after a sign; and there shall no sign be given to it, but the sign of the prophet Jonas:
The only sign to be given them is shown in the Prophet Jonas
Mat 12:40 For as Jonas was three days and three nights in the whale's belly; so shall the Son of man be three days and three nights in the heart of the earth.
So the death and burial of Jesus Christ (or Similitude of the same). He continues concerning the very preaching of Jonah and the men of Nineveh's response in repenting when he says,
Mat 12:41 The men of Nineveh shall rise in judgment with this generation, and shall condemn it: because they repented at the preaching of Jonas; and, behold, a greater than Jonas is here.
Whereas the Apostles say, Jesus (a greater then Jonas) was sent unto them in like manner to bless them (first) in this way
Acts 3:26 Unto you first God, having raised up his Son Jesus, sent him to bless you, in turning away every one of you from his iniquities. (See 2 Ti 2:19 also)
And as His Father sent him so also sends he them, Paul saying,
Col 1:28 Whom we preach, warning every man, and teaching every man in all wisdom; that we may present every man perfect in Christ Jesus.
In respects to someones blood, or requiring it at the watchman's hand for not blowing the trumpet / warning a people is also shown here
Ezek 33:6 But if the watchman see the sword come, and blow not the trumpet, and the people be not warned; if the sword come, and take any person from among them, he is taken away in his iniquity; but his blood will I require at the watchman's hand.
Whereas Paul had said similarly
Acts 20:26 Wherefore I take you to record this day, that I am pure from the blood of all men.
Acts 20:27 For I have not shunned to declare unto you all the counsel of God.
Col 1:28 Whom we preach, warning every man, and teaching every man in all wisdom; that we may present every man perfect in Christ Jesus.
Earlier it shows Jesus sending his into every city and the woes that follow those who would not listen
Luke 10:1 After these things the Lord appointed other seventy also, and sent them two and two before his face into every city and place, whither he himself would come.
Luke 10:10 But into whatsoever city ye enter, and they receive you not, go your ways out into the streets of the same, and say,
Luke 10:11 Even the very dust of your city, which cleaveth on us, we do wipe off against you: notwithstanding be ye sure of this, that the kingdom of God is come nigh unto you.
Luke 10:12 But I say unto you, that it shall be more tolerable in that day for Sodom, than for that city.
Luke 10:13 Woe unto thee, Chorazin! woe unto thee, Bethsaida! for if the mighty works had been done in Tyre and Sidon, which have been done in you, they had a great while ago repented, sitting in sackcloth and ashes.
Luke 10:14 But it shall be more tolerable for Tyre and Sidon at the judgment, than for you.
Luke 10:15 And thou, Capernaum, which art exalted to heaven, shalt be thrust down to hell.
Luke 10:16 He that heareth you heareth me; and he that despiseth you despiseth me; and he that despiseth me despiseth him that sent me.
Again, it just follows a pattern of sending his to preach
Acts 20:26-27 Wherefore I take you to record this day, that I am pure from the blood of all men. For I have not shunned to declare unto you all the counsel of God.
Just as Paul preaches faith in Christ to Felix in Acts 24:25
As he (Paul) reasoned of righteousness, temperance, and judgment to come,
But this is just not a convenient season for Felix
Felix trembled, and answered,
Go thy way for this time; when I have a convenient season, I will call for thee.
Nineveh repented at the preaching of Jonah Mat 12:41 God also having raised up his Son Jesus, sent him to bless them, in turning away every one of them from his iniquities Acts 3:26
Moral of the story could be pretty important here