Believing in Resurrection as a religious principle
Some disbelieve in Resurrection and retuning to God after death , therefore they do not admit prophecy as a religious principle as a result they will spend all their time for making their worldly life rather the spiritual life , they think they have an everlasting life:
1- Those who do not expect to meet us and are pleased with worldly life and feel at ease about it, as well as those who are heedless of our signs will find their logging in the fire because of what they have been earning. (10:7-8)
2- So shun anyone who avoids mentioning us and only wants [to enjoy] worldly life, that will be their range of knowledge. Your Lord is quite Aware as to who has strayed from his path.(53:29-30)
3- Those who stray from Gods path will have severe torment because they have forgotten they Day of Reckoning!(38:26)
According to the Koran perfect monotheism requires believing in Resurrection
Your God is God Alone! Those who do not believe in the Hereafter have hearts which refuse to learn which they are over proud.(16:22)
Sources :
"al-Mizan" (Allameh Tabatabi)
The Quran (T.B. Irving)