John Calvin on John 16:20

20. You will weep and lament. He shows for what reason he foretold that his departure was at hand, and, at the same time, added a promise about his speedy return. It was, that they might understand better that the aid of the Spirit was highly necessary. “A hard and severe temptation,” says he, “awaits you; for, when I shall be removed from you by death, the world will proclaim its triumphs over you. You will feel the deepest anguish. The world will pronounce itself to be happy, and you to be miserable. I have resolved, therefore, to furnish you with the necessary arms for this warfare.” He describes the interval that elapsed between his death and the day when the Holy Spirit was sent; “Et le jour que le S. Esprit fut envoye.” for at that time their faith, so to speak, lay prostrate and exhausted.

Your sorrow will be turned into joy. He means the joy which they felt after having received the Spirit; not that they were afterwards free from all sorrow, but that all the sorrow which they would endure was, swallowed up by spiritual joy We know that the apostles: so long as they lived, sustained a severe warfare, that they endured base reproaches, that they had many reasons for weeping and lamenting; but, renewed by the Spirit, they had laid aside their former consciousness of weakness, so that, with lofty heroism, they nobly trampled under foot all the evils that they endured. Here then is a comparison between their present weakness and the power of the Spirit, which would soon be given to them; for, though they were nearly overwhelmed for a time, yet afterwards they not only fought bravely, but obtained a glorious triumph in the midst of their struggles. Yet it ought also to be observed, that he points out not only the interval that elapsed between the resurrection of Christ and the death of the apostles, but also the period which followed afterwards; as if Christ had said, “You will lie prostrate, as it were, for a short time; but when the Holy Spirit shall have raised you up again, then will begin a new joy, which will continue to increase, until, having been received into the heavenly glory, you shall have perfect joy.”

John 16:21-24

21. A woman, when she is in labor, hath sorrow, because her hour is come; but when she hath brought forth a child, she remembereth no more her anguish, on account of the joy that a man is born into the world. 22. And you therefore have sorrow now; but I will see you again, and your heart will rejoice, and your joy no man shall take from you. 23. And in that day you will ask me nothing. Verily, verily, I tell you, That whatever you shall ask from the Father in my name, he will give to you. 24. Hitherto you have asked nothing in my name: ask, and receive, that your joy may be full.