The soul is the principle of life, which leaves the body at the moment of death. Human life is not the individual's property but a divine gift to be used in God's service or to be dedicated to a divine cause or to God Himself. Death is no longer the end of life, but only the end of the appointed period (ajal) in which humans are tested in the world. Death in this perspective is simply the end of a testing period and a threshold, which must necessarily passed. Human existence has been extended to eternity and death becomes a merely transitional phase during which the soul provisionally remains separated from the disintegrating body.
The Koran takes the human fear of death for granted. Death is the great of humankind, which overtakes (adraka) even those who seek refuge in lofty towers (4:78). Death need be feared only by those who have led evil lives. Those who have given witness of their belief by dying as martyrs should be thought of not as dead but as living (2:154, 3:169). An unbeliever, however, clings to this life and believes death to be the inevitable result of fate (dahr). Unbelievers who do not believe in the resurrection are only concerned with life in this world (6:29, 23:37). The Koran describes vividly the last moments of their lives (6:93, 33:19, 47:20, 56:83) and their agony (50:19). Angels of death stretch out their hands and speak to them while they are dying (6:93). Those attached to this world flee death in vain. One text, however, describes how in a particular case God had pity on thousands of people who, threatened by death, left their houses (2:243). The word za'ika means taste, occurring three times in the Koran: "Every soul shall taste of death" (3:184), "Every soul must taste of death" (21:35) and "Every soul must taste of death" (27:57). Thus, with Islam, death is no longer the end of life, but only the end of the appointed period (ajal) in which humans are tested in the world.
Hasan bin Ali bin Abu Talib said, "Death is a greatest joy, which comes upon the believers when they go from this house of affliction to eternal bliss. And it is the greatest tribulation, which comes upon the infidels when they go from their paradise (earth) to a fire which abates not, nor is it extinguished."
According to Risalatu'l I'tiqadati'l Imamiya, Imam Zayn al-Abidin was asked, what is death? He said, "For the believer it is like taking off clothes which are dirty and lousy or breaking heavy shackles and fetters, and changing into the most gorgeous and perfumed of apparel, and (riding on) well-trained mounts, and (alighting in) familiar resting places. And for the unbeliever, it is the pulling off of gorgeous apparel and changing into the most filthy and coarse clothing; and the transportation from familiar places to the wildest resting places and the greatest torment."
Imam Muhammad al-Bakir said, "It (death) is the sleep which comes to you every night, except that it is of long duration. The sleeper does not awake from it except on the day of resurrection. Some see in their sleep certain kinds of joy the worth whereof cannot be estimated; others, certain kinds of terror, which are beyond the pale of estimation. How then can his condition (be described) who may be happy or fearful in death? This then death, so be prepared for it." Imam Jafar Sadik said, "To the believer, death is like the most perfumed breeze, which he inhales and then doses off on account of the perfume, and his weariness, and pain disappear from him. To the unbeliever it is like the biting of vipers and the stinging of scorpions; nay, it is even more painful. Imam Jafar Sadik relates that once a man went to Abu Dharr al-Ghifari and asked, why is it that we dislike death? He said, "Because you have built for this world and ruined (your prospects for) the next, and men dislike shifting from a settled habitation to a ruin."
Mention of the word “death” whips up emotions of fear and sadness in most people. This is quite natural, because biological death marks the end of physical life on earth. To people, who are preoccupied with material things and sensual delights, death represents an end to all that. Religion aims to awaken in human beings the realization that while life on this earth is short and transient, it has immense potentialities to achieve higher spiritual stations that lead to life eternal. The Koran says, “This life of the world is but a pastime and a game. Lo! the home of the hereafter – that is life, if they but knew” (29:64). The Prophet also said, “This life on earth is a slumber, death marks the awakening of the soul.”