Luke 6:21b FNV
"You weep now, are often in tears, tears of repentance, tears of sympathy; you are of them that mourn in Zion. But blessed are you; your present sorrows are no prejudices to your future joy, but preparatories for it: You shall laugh. You have triumphs in reserve; you are but sowing in tears, and shall shortly reap in joy," Ps. 126:5, 6. They that now sorrow after a godly sort are treasuring up comforts for themselves, or, rather, God is treasuring up comforts for them; and the day is coming when their mouth shall be filled with laughing and their lips with rejoicing, Job 8:21.
You that are in a sad, afflicted state (being my disciples) are blessed; for there will come a time when God shall wipe tears from your eyes.
[Excerpt from Matthew Henry's Full Commentary & Matthew Poole's Commentary]