Here is a woe to them that laugh now, that have always a disposition to be merry, and always something to make merry with; that know no other joy than that which is carnal and sensual, and know no other use of this world’s good than purely to indulge that carnal sensual joy that banishes sorrow, even godly sorrow, from their minds, and are always entertaining themselves with the laughter of the fool. Woe unto such, for it is but now, for a little time, that they laugh; they shall mourn and weep shortly, shall mourn and weep eternally, in a world where there is nothing but weeping and wailing, endless, easeless, and remediless sorrow.
That laugh now - Are happy, or thoughtless, or joyful, or filled with levity.
Shall mourn and weep - The time is coming when you shall sorrow deeply. In sickness, in calamity, in the prospect of death, in the fear of eternity, your laughter shall be turned into sorrow. "There is" a place where you cannot laugh, and there you will see the folly of having passed the "proper time" of preparing for such scenes in levity and folly. Alas! how many thus spend their youth! and how many weep when it is too late! God gives them over, and "laughs" at their "calamity," and mocks when their fear comes, Proverbs 1:26. To be happy in "such scenes," it is necessary to be sober, humble, pious in early life. "Then" we need not weep in the day of calamity; then there will be no terror in death; then there will be nothing to fear in the grave.
[Excerpt from Matthew Henry's Full Commentary & Barnes' Notes]