In the Name of Allah , the Compassionate , the Merciful
The Holy Prophet [s] said: "During the third part of every night and on the night before Friday from the beginning (until the break of dawn) Allah sends an angel unto the sky of the earth in order to call: 'Is there any needy who asks that I may bestow upon him his need? Is there any repentant one that I may return to him? Is there any seeker of forgiveness that I may forgive him?'"
Islamic traditions teach that sleeping on the night before Friday is called 'the regret sleep'; for, on the Reckoning Day, people will regret very much that they had been asleep on the nights before Fridays.
Bihar-ul-Anwar, vol. 3, p. 314