Matthew 12:38-41
38 Then some of the scribes and Pharisees said to him, “Teacher, we wish to see a sign from you.” 39 But he answered them, “An evil and adulterous generation asks for a sign, but no sign will be given to it except the sign of the prophet Jonah. 40 For just as Jonah was three days and three nights in the belly of the sea monster, so for three days and three nights the Son of Man will be in the heart of the earth. 41 The people of Nineveh will rise up at the judgment with this generation and condemn it, because they repented at the proclamation of Jonah, and see, something greater than Jonah is here!

Jonah 1:17
But the Lord provided a large fish to swallow up Jonah; and Jonah was in the belly of the fish three days and three nights.

Jonah Ch. 2 (NRSV)
Then Jonah prayed to the Lord his God from the belly of the fish, 2 saying,

“I called to the Lord out of my distress,
and he answered me;
out of the belly of Sheol I cried,
and you heard my voice.
3 You cast me into the deep,
into the heart of the seas,
and the flood surrounded me;
all your waves and your billows
passed over me.
4 Then I said, ‘I am driven away
from your sight;
how shall I look again
upon your holy temple?’
5 The waters closed in over me;
the deep surrounded me;
weeds were wrapped around my head
6 at the roots of the mountains.
I went down to the land
whose bars closed upon me forever;
yet you brought up my life from the Pit,
O Lord my God.
7 As my life was ebbing away,
I remembered the Lord;
and my prayer came to you,
into your holy temple.
8 Those who worship vain idols
forsake their true loyalty.
9 But I with the voice of thanksgiving
will sacrifice to you;
what I have vowed I will pay.
Deliverance belongs to the Lord!”
10 Then the Lord spoke to the fish, and it spewed Jonah out upon the dry land.