It was the custom of Hadhrat ‘Ali (May Allah be well pleased with him) that he would spend the night in worship and prayer:
Translation: Once Hadhrat Ashtar Nakha’ee (May Allah shower His mercy on him) called upon the Commander of the Faithful, Hadhrat ‘Ali (May Allah be well pleased with him). At that time, he was engaged in Salaat. He said: O Commander of the Faithful! You fast in the day and stand in worship in the night. Between these 2, you are taxing yourself. After Salaat, when Hadhrat ‘Ali (May Allah be well pleased with him) heard this, he said: The journey of the hereafter is very long. To traverse it, worship of the night is highly essential for a human being. (Seerah Ameer Ul Momineen ‘Ali bin Abi Talib Razi Allahu Anhu, Vol. 1, Pg. No. 344)
Abul Hasanaat Islamic Research Center 