John 16:20
“Verily, verily, I say unto you, That you shall weep and lament”—which belonged to the Death and the Cross—“but the world shall rejoice.”
Because by reason of their not desiring His death, they quickly ran into the belief that He would not die, and then when they heard that He would die, cast about, not knowing what that “little” meant, He says, “You shall mourn and lament.”
“But your sorrow shall be turned into joy.” Then having shown that after grief comes joy, and that grief genders joy, and that grief is short, but the pleasure endless, He passes to a common example; and what says He?
Source: Homilies on the Gospel of John (New Advent)