Prophet Abraham - 14:22
"After the decision was published, Satan said to them: "Allah has promised you the truth, but I promised you and broke my word. I had no power over you; I called you and you joined me. So do not condemn me, but only condemn yourselves. You cannot save me, nor can I save you. I have already denied your associating me as a partner, and for the wrongdoers there is a painful torment."
Why does Allah not forgive those who die associating partners?
The Women/4:48
Allah does not forgive associating partners with Him, but other than that He forgives to whom He wills. Whoever associates partners with Allah has committed a great insult.
The Women/4:116
Allah does not forgive associating partners with Him (if it continues until death), but He forgives the sins below that to whom He wills. Whoever associates partners with Allah has gone astray.
Luqman/31:13
"When Lokman advised his son, he said: "My dear son, do not associate partners with Allah; surely shirk (associating partners with God) is a great wrong."
The Companies/39:65
It has been revealed to you and those before you that if you associate partners, all that you do will be in vain and you will be of the losers.