Is repentance obligatory for someone who lied in jest and forgot to clarify the truth?

It is not permissible to fabricate false stories to make people laugh, as lying is forbidden. The matter becomes more serious if it involves mockery of religion, which could amount to disbelief that expels one from the fold of Islam. Therefore, one must hasten to sincere repentance with its conditions: sincerity of repentance to Allah, regret over the sin, abandoning it, resolving not to return to it, and that repentance occurs before gurgling (death throes) and before the sun rises from the west.