You have to read the Book of Daniel to understand what the unforgivable sin is!
Here is a hint:
Another word for sin is "transgression"
A transgression which causes desolation is a sin that is not forgiven.
Daniel 8:13-14
And I got to hear a certain holy one speaking, and another holy one proceeded to say to the particular one who was speaking: "How long will the vision be of the constant [feature] and of the transgression causing desolation, to make both [the] holy place and [the] army things to trample on?" 14 So he said to me: "Until two thousand three hundred evenings [and] mornings; and [the] holy place will certainly be brought into its right condition."
Daniel 11:31
And there will be arms that will stand up, proceeding from him; and they will actually profane the sanctuary, the fortress, and remove the constant [feature].
"And they will certainly put in place the disgusting thing that is causing desolation. (not forgiven)
Daniel 9:24
"There are seventy weeks that have been determined upon your people and upon your holy city, in order to terminate the transgression,
Matthew 13:40-43
.The Son of man will send forth his angels, and they will collect out from his kingdom all things that cause stumbling and persons who are doing lawlessness, 42 and they will pitch them into the fiery furnace. There is where [their] weeping and the gnashing of [their] teeth will be. 43 At that time the righteous ones will shine as brightly as the sun in the kingdom of their Father. Let him that has ears listen.
abe