Generally, death is defined as the separation of the immortal soul from the mortal body. Moreover, Christians believe that after death, the souls goes to heaven or hell, depending upon their belief or non-belief in God.
In Heaven, individuals enjoy in the presence of God and in Hell, they suffer eternally for their sins. In addition, Catholic Christians believe in purgatory, i.e., a place for temporary punishment for purification to be made ready for Heaven.
You can read about purgatory at Wikipedia. Death is often explained as the result of sin. As stated in Genesis 2:17, “But of the tree of the knowledge of good and evil, thou shalt not eat of it: for in the day that thou eatest thereof thou shalt surely die.”
Hence, it is believed that the phenomenon of death came into effect due to the devil’s envy and Adam and Eve’s disobedience. However, that innocent people also die is a fact.
Consequently, death seems to be a necessity as it releases man from mortal life on earth to immortality in the presence of God in a spiritualized body.
Jesus Christ conquered death by His Resurrection and assured victory over death for those who choose to abide by the Will of God and give up their own selfish and whimsical desires.
As John 11:25-26 declares, “I (Jesus) am the resurrection and the life. He who believes in me will live, even though he dies; and whoever lives and believes in me will never die.”
Death Quotes From The Bible
“Therefore, brothers and sisters, we have an obligation—but it is not to the flesh, to live according to it. For if you live according to the flesh, you will die; but if by the Spirit you put to death the misdeeds of the body, you will live.” – Romans 8:12-13
“Precious in the sight of God is the death of His saints.” – Psalm 116:15
“Then shall the dust return to the earth as it was: and the spirit shall return unto God who gave it.” – Ecclesiastes 12:7
“For as the body without the spirit is dead, so faith without works is dead also.” – James 2:26
“There is a time for everything, and a season for every activity under the heavens: a time to be born and a time to die; a time to plant, and a time to pluck up that which is planted;” – Ecclesiastes 3:2
“When the perishable puts on the imperishable, and the mortal puts on immortality, then shall come to pass the saying that is written: “Death is swallowed up in victory.” “O death, where is your victory? O death, where is your sting?” The sting of death is sin, and the power of sin is the law. But thanks be to God, who gives us the victory through our Lord Jesus Christ.” – Corinthians 15:54-57
“Likewise, my brothers, you also have died to the law through the body of Christ, so that you may belong to another, to him who has been raised from the dead, in order that we may bear fruit for God.” – Romans 7:4
“For to me, to live is Christ, and to die is gain. But if I live on in the flesh, this will mean fruit from my labor; yet what I shall choose I cannot tell. For I am hard-pressed between the two, having a desire to depart and be with Christ, which is far better.” – Philippians 1:21-23
You can read more about physical and spiritual death here. Besides, at www.biblicalperspectives.com, you can find a detailed study on the Biblical View Of Death by Samuele Bacchiocchi, Ph. D., Andrews University.