But on the Day [of Judgment], they who had attained to faith will [be able to] laugh at the [erstwhile] deniers of the truth:

But on this Day the Believers will laugh at the Unbelievers:

This day it is those who believe who have the laugh of disbelievers,

So this day those who believe laugh at the disbelievers --

So Today those who believed are laughing at the disbelievers,