Reference: http://www.alfawzan.af.org.sa/node/16100
Question: What is the ruling about saying ‘O Allaah! Hasten the arrival of the Last Hour’?
Response: [This is] not legislated; this supplication is not legislated. However, instead he should ask Allaah for success, guidance, and righteous action[s]. As for [asking for hastening the arrival of] the Last Hour – then this [matter] is in the Hands of Allaah سبحانه و تعالى, and it will not be brought forward or delayed from its appointed time which Allaah سبحانه و تعالى has decreed for it.
