Students of Scripture always point out that John has no miracles in his gospel; he only has "signs." Already in chapter 2, at the wedding reception in Cana of Galilee, the evangelist mentions that Jesus performed "the first of his signs" to save a newly married from embarrassment. John never refers to Jesus' changing water into wine as a miracle.
Webster defines a sign as "something (such as an action or event) which shows that something else exists, is true, or will happen." That's how John employs miracles. They're actions pointing not to themselves, but to something else. Whenever Jesus works a miracle in John, we always have to ask, "What's the deeper meaning?" We only understand John's miracles when we go beyond their face value.
Though most Christians, for instance, know the basics of Jesus raising his friend Lazarus from the dead, many have no idea what John is trying to convey by narrating it. They miss where the sign is pointing.
The fourth evangelist is a proponent of "realized eschatology." In other words, he's convinced that whatever most followers of Jesus once believed would happen only when Jesus returns in the Second Coming, or when a Christian dies, we already have right here and now. Raising Lazarus is a sign of that belief.
Notice the interchange between Martha and Jesus. Jesus assures her, "Your brother will rise." Martha replies, "I know he will rise, in the resurrection on the last day." Jesus then tells her, "I am the resurrection and the life; those who believe in me, even if they die, will live, and everyone who lives and believes in me will never die." Then, the $64,000 question: "Do you believe this?"
Within a short period of time, Jesus gives a sign that those who believe in him are already alive even before their physical deaths by calling Lazarus from his tomb.
Ezekiel, in today's first reading, doesn't quite employ realized eschatology when he speaks Yahweh's word to the Jewish captives during the Babylonian Exile. But he does something similar. Because the prophet must make God's promise of a return to the Holy Land meaningful to those who will die before the event happens, he poetically quotes Yahweh, "I will open your graves and have you rise from them, and bring you back to the land of Israel." Scripture scholars presume Ezekiel's audience didn't take these words literally. They simply were meant to give them hope that they would return to Israel in the person of their children and grandchildren who actually would experience that longed-for event. Though dead, all who heard Ezekiel would be alive in the person of their descendants.
Paul treats this alive/though dead idea from a different direction. Writing to the Christian community in Rome, he distinguishes between the life the Spirit instills in imitators of the risen Jesus and the many deaths our human bodies must endure. "If Christ is in you," he contends, "although the body is dead because of sin, the spirit is alive because of righteousness." In other words, if you're doing what God wishes you to do by becoming other Christs, you have the same spirit living in you that the risen Jesus has living in him/her.
But, getting back to John's realized eschatology, commentators usually mention that though the evangelist believes what will happen at the end is already here, it's not here exactly as it will be in the end. To convey this concept they employ the term "already, but not yet."
I presume Jesus crying at his friend's tomb is an essential part of the not yet; a sign for us that our "alreadys" will always include a lot of tears.