15 “He that believes in me, though he were dead, yet shall he live: and whosoever lives and believes in me shall never die.” What means this? “He that believes in me, though he were dead,” just as Lazarus is dead, “yet shall he live;” for He is not the God of the dead, but of the living. Such was the answer He gave the Jews concerning their fathers, long ago dead, that is, concerning Abraham, and Isaac, and Jacob: I am the God of Abraham, and the God of Isaac, and the God of Jacob: He is not the God of the dead, but of the living; for all live unto Him. Believe then, and though thou were dead, yet shall you live: but if you believe not, even while you live you are dead. Let us prove this likewise, that if you believe not, though you live you are dead. To one who was delaying to follow Him, and saying, “Let me first go and bury my father,” the Lord said, “Let the dead bury their dead; but come thou and follow me.” There was there a dead man requiring to be buried, there were there also dead men to bury the dead: the one was dead in the flesh, the others in soul. And how comes death on the soul? When faith is wanting. How comes death on the body? When the soul is wanting. Therefore your soul's soul is faith. “He that believes in me,” says Christ, though he were dead in the flesh, yet shall he live in the spirit; till the flesh also rise again, never more to die. This is “he that believes in me,” though he die, “yet shall he live. And whosoever lives” in the flesh, “and believes in me,” though he shall die in time on account of the death of the flesh, “shall never die,” because of the life of the spirit, and the immortality of the resurrection. Such is the meaning of the words, “And whosoever lives and believes in me shall never die. Believest thou this? She says unto Him, Yea, Lord, I have believed that You are the Christ, the Son of God, who hast come into the world.” When I believed this, I believed that You are the resurrection, that You are the life: I believed that he that believes in You, though he die, yet shall he live; and whosoever lives and believes in You, shall never die.
16. “And when she had so said, she went her way, and called Mary her sister silently, saying, The Master has come, and calls for you.” It is worthy of notice the way in which the whispering of her voice was denominated silence. For how could she be silent, when she said, “The Master has come, and calls for you”? It is also to be noticed why it is that the evangelist has not said where, or when, or how the Lord called for Mary; namely, that in order to preserve the brevity of the narrative, it may rather be understood from the words of Martha.
17. “As soon as she heard that, she arose quickly, and came unto Him. For Jesus was not yet come into the town, but was still in that place where Martha met Him. The Jews, then, who were with her in the house, and comforted her, when they saw Mary, that she rose up hastily, and went out, followed her, saying, She goes unto the grave, to weep there.” What cause had the evangelist to tell us this? To show us what it was that occasioned the numerous concourse of people to be there when Lazarus was raised to life. For the Jews, thinking that her reason for hastening away was to seek in weeping the solace of her grief, followed her; that the great miracle of one rising again who had been four days dead, might have the presence of many witnesses.
18. “Then when Mary had come where Jesus was, and saw Him, she fell down at His feet, saying unto Him, Lord, if You had been here, my brother had not died. When Jesus therefore saw her weeping, and the Jews also weeping, who were with her, He groaned in the spirit, and troubled Himself, and said, Where have ye laid him?” Something there is, did we but know it, that He has suggested to us by groaning in the spirit, and troubling Himself. For who could trouble Him, save He Himself? Therefore, my brethren, first give heed here to the power that did so, and then look for the meaning. You are troubled against your will; Christ was troubled because He willed. Jesus hungered, it is true, but because He willed; Jesus slept, it is true, but because He willed; He was sorrowful, it is true, but because He willed; He died, it is true, but because He willed: in His own power it lay to be thus and thus affected or not. For the Word assumed soul and flesh, fitting on Himself our whole human nature in the oneness of His person. For the soul of the apostle was illuminated by the Word; so was the soul of Peter, the soul of Paul, of the other apostles, and the holy prophets—the souls of all were illuminated by the Word; but of none was it said, “The Word was made flesh;” of none was it said, I and the Father are one. The soul and flesh of Christ is one person with the Word of God, one Christ. And by this [Word] wherein resided the supreme power, was infirmity made use of at the beck of His will; and in this way “He troubled Himself.”
Source: Tractates on the Gospel of John (New Advent)