It is narrated from the Mother of the Believers, Sayyidah Aishah (may Allah be pleased with her), that the Prophet (peace and blessings be upon him) said: "Any person who has the habit of praying at night (tahajjud), and (on some night) sleep overcomes him, Allah, the Mighty and Majestic, writes for him the reward of his prayer, and that sleep of his is a charity for him."
Imam al-Tabarani (may Allah have mercy on him) said: "No one narrated this hadith from Ziyad (may Allah have mercy on him) except Muslim (may Allah have mercy on him), and Ali (may Allah have mercy on him) is alone in narrating it."
Hadith Referenceالمعجم الأوسط / باب الألف / 1338
Hadith Takhrij«أخرجه مالك فى «الموطأ» برقم: 385 / 113، والنسائي فى «المجتبى» برقم: 1783 / 1، 1784 / 1، 1785 / 2، والنسائي فى «السنن الكبرى» برقم: 1461، 1462، وأبو داود فى «سننه» برقم: 1314، والبيهقي فى «السنن الكبرى» برقم: 4798، وأحمد فى «مسنده» برقم: 24979، 25079، 26101، والطيالسي فى «مسنده» برقم: 1631، والطبراني فى «الأوسط» برقم: 6172»