The Prophets - 21:98 You and those whom you serve besides Allah are the fuel of Hell; you are worthy to enter it.
Why does Allah not forgive those who die serving others other than Him?
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.