I Am the Resurrection and the Life
Jesus’ concern is to divert Martha’s focus from an abstract belief in what takes place on the last day, to a personalized belief in him who alone can provide it. Just as he not only gives the bread from heaven (6:27) but is himself the bread of life (6:35), so also he not only raises the dead on the last day (5:21, 25ff.) but is himself the resurrection and the life. There is neither resurrection nor eternal life outside of him.
Resurrection
The plain reference of resurrection is to the final resurrection of believers at the last day, through Christ whose power effects it
The Heidelberg Catechism:
Question 1
What is thy only comfort in life and death?
That I with body and soul, both in life and death,a am not my own,b but belong unto my faithful Saviour Jesus Christ;c who, with his precious blood, has fully satisfied for all my sins,d and delivered me from all the power of the devil;e and so preserves mef that without the will of my heavenly Father, not a hair can fall from my head;g yea, that all things must be subservient to my salvation,h and therefore, by his Holy Spirit, He also assures me of eternal life,i and makes me sincerely willing and ready, henceforth, to live unto him.j
life
The verb lives cannot simply mean is alive, as the triteness would be unbearable; obviously only those who are alive can believe! We have repeatedly noticed that the background for these verses is 5:21ff., and there the notion of life is invariably the life of God, saving life, eternal life, the life of the kingdom. So also here: we might paraphrase, ‘whoever has eternal life and believes in me will never die’. The two descriptions ‘has eternal life’ and ‘believes in me’ are not tautologous. The first stresses the internal change that must come about, wrought by the power of God (viz. he lives, he has eternal life); the second underlines what stance the individual must adopt (viz. he believes)