On the authority of al-Baraa ibn ‘Aazib (radhi-yallaahu ‘anhu) who said: While we were with the Messenger of Allaah (sal-Allaahu `alayhe wa sallam), he suddenly looked towards a group (of people) and said:
“For what reason have they gathered here?”
It was said: In order to dig a grave.
So the Messenger of Allaah (sal-Allaahu `alayhe wa sallam) became alarmed and startled and he quickly went ahead of his Companions until he reached the grave, then he knelt upon it, and I turned my face towards him (sal-Allaahu `alayhe wa sallam), in order to see what he was doing. He (sal-Allaahu `alayhe wa sallam) cried until the earth became wet with his tears, then he turned to us and said:
“O my brothers! Prepare for a day like this”