Hazrat Ali A.S said:
A time will come when evil will be extensively prevalent. At that time, the crescent will appear unusually bigger as if it were two nights old, at times it will not even be seen and will be so hidden that people will not fast on the first day of Ramazan and on account of not seeing the crescent they will fast on the Eid day.
Then save yourselves, please save yourselves in those times. Allah will punish people at that time due to their negligence. Indeed in those days sudden deaths will be current amongst people. Death will attack people so quickly that a person who is sound and healthy in the morning will be in his grave by the evening. He will be absolutely alright in the evening, but will be a corpse in the morning. So in such a time it is incumbent on people to keep ready their last will and testament before the coming of the trouble and offer their prayers early in right time because there Is always a fear that perhaps death may overtake them suddenly. Then whoever from you reaches such a generation should not sleep at night but with Taharat and remain in Taharat all the time.