World Wide Study Bible
a Bible passage
15. And I rejoice, on your account, that I was not there. He means that his absence was profitable to them, because his power would have been less illustriously displayed, if he had instantly given assistance to Lazarus. For the more nearly the works of God approach to the ordinary course of nature, the less highly are they valued, and the less illustriously is their glory displayed. This is what we experience daily; for if God immediately stretches out his hand, we do not perceive his assistance. That the resurrection of Lazarus, therefore, might be acknowledged by the disciples to be truly a Divine work, it must be delayed, that it might be very widely removed from a human remedy.
We ought to remember, however, what I formerly observed, that the fatherly kindness of God towards us is here represented in the person of Christ. When God permits us to be overwhelmed with distresses, and to languish long under them, let us know that, in this manner, he promotes our salvation. At such a time, no doubt, we groan and are perplexed and sorrowful, but the Lord rejoices on account of our benefit, and gives a twofold display of his kindness to us in this respect, that he not only pardons our sins, but gladly finds means of correcting them.
That you may believe. He does not mean that this was the first feeble commencement of faith in them, but that it was a confirmation of faith already begun, though it was still exceedingly small and weak. Yet he indirectly suggests that, if the hand of God had not been openly displayed, they would not have believed.