‘But when Jesus heard it he said, “This sickness is not unto death, but for the glory of God, that the Son of God may be glorified thereby”.'
Jesus' reply was that the sickness would not finally be terminal, at least from His point of view. “It is for the glory of God, so that the Son of God might be glorified by means of it”. This statement was pregnant with meaning. Not only would God be glorified through it, but the glory of Jesus as the Son of God would also be revealed. Jesus knew that the incident would have widespread effects. He knew that Lazarus was, in fact, going to die, but He also knew that He would raise him from death. The whole incident was to be a means by which the God's glory would be manifested, and the glorious reality of the resurrection would be revealed in picture form. But it would also be an incident which would arouse His enemies and finally result in His death, because they were so blinded that, instead of glorying in a wonderful miracle, they resented the influence that it gave Him (John 11:45-53). Although in contrast to this was the fact that some did believe (John 11:45).
Thus Jesus specifically declared that by it He, ‘the Son of God' (the God-sent Messianic prince, the only true Son of God) would be glorified in two senses. Firstly in that His power to raise the dead, including the dead at the last day, would be amazingly revealed. But secondly because through it He would be glorified by being raised up on a cross, in order that through His death He might perform the work that would make the resurrection possible (John 12:23). He was both challenging the power of death and challenging His adversaries, knowing in both cases what the consequences would be.
From John 11:40 we are also probably to gather that these words were sent to Mary and Martha as an encouragement in their distress.
The term ‘Son of God' would be understood by listeners as signifying the One chosen and appointed by God. To Jesus and to the readers, in the light of chapter 1 and often, it signifies that He is God's only Son.