Humans are mortal, a word derived from the Latin mortalis, meaning death. God could have created humans as immortal right from the start, as He did with the angels, so that we could live on and on forever no matter what, but He didn't. God deliberately created us so that we can die, totally die, for the same reason that computers can delete corrupt or malicious files. Those who choose to repent and obey God, on His terms, will be made immortal, never again subject to illness, injury or death, while those who choose to rebel and defy God will be completely erased forever (see Resurrections).

Old Testament

The people of the Old Testament were well aware of the human potential for immortality:

"Thou dost guide me with Thy counsel, and afterward Thou wilt receive me to glory." (Psalm 73:24 RSV)

"By faith Abraham obeyed when he was called to go out to a place which he was to receive as an inheritance; and he went out, not knowing where he was to go. By faith he sojourned in the land of promise, as in a foreign land, living in tents with Isaac and Jacob, heirs with him of the same promise. For he looked forward to the city which has foundations, whose builder and maker is God. By faith Sarah herself received power to conceive, even when she was past the age, since she considered him faithful who had promised. Therefore from one man, and him as good as dead, were born descendants as many as the stars of heaven and as the innumerable grains of sand by the seashore. These all died in faith, not having received what was promised, but having seen it and greeted it from afar, and having acknowledged that they were strangers and exiles on the earth." (Hebrews 11:8-13 RSV)

New Testament

With the coming of Jesus Christ, the means of finding immortality was made more clear:

"the power of God, Who saved us and called us with a holy calling, not in virtue of our works but in virtue of His own purpose and the grace which He gave us in Christ Jesus ages ago, and now has manifested through the appearing of our Savior Christ Jesus, Who abolished death and brought life and immortality to light through the gospel." (2 Timothy 1:8-10 RSV)

"For he will render to every man according to his works: to those who by patience in well-doing seek for glory and honor and immortality, He will give eternal life; but for those who are factious and do not obey the truth, but obey wickedness, there will be wrath and fury." (Romans 2:6-8 RSV)

Fact Finder: Can humans be granted eternal life just by having faith alone?
See Works