Yes, it is true that all of the Prophets of God (Allah), including Adam, Noah, Abraham, Moses, and Jesus, among others, warned their people about the importance of preparing for death and the afterlife. They taught their followers about the consequences of their actions in this life and how they will be held accountable for their deeds in the next life.

"And We certainly sent into every nation a messenger, [saying], 'Worship Allah and avoid Taghut.' And among them were those whom Allah guided, and among them were those upon whom error was [deservedly] decreed. So proceed through the earth and observe how was the end of the deniers." - Quran 16:36

In Islam, death is seen as the separation of the soul from the body, and it is believed that the afterlife is a continuation of the soul's journey. Muslims believe that after death, the soul is taken to Barzakh, an intermediary state, where it waits until the Day of Judgment.

On the Day of Judgment, all souls will be resurrected, judged according to their deeds, and rewarded or punished accordingly. Those who have led righteous lives and followed the path of God will be rewarded with paradise (Jannah) and those who have led unrighteous lives will be punished in hell (Jahannam).

The concept of the afterlife is a central tenet of Islam and is based on the belief in the existence of a merciful and just God who rewards good deeds and punishes wrongdoing. Muslims believe that good deeds will be rewarded even after death and that people should strive to live their lives in the best way possible, with the hope of gaining God's favor and mercy in the afterlife.

"Say, 'Indeed, the death from which you flee - indeed, it will meet you. Then you will be returned to the Knower of the unseen and the seen, and He will inform you about what you used to do." - Quran 62:8