It is narrated from Abdur Rahman bin Aswad, his father asked Sayyida Aisha (may Allah be pleased with her) what the Messenger of Allah (peace and blessings be upon him) used to do if he wished to sleep in a state of major ritual impurity (janabah)? She replied: He would perform ablution (wudu) like that for prayer, and then he would sleep.
Hadith Referenceسنن دارمي / من كتاب الطهارة / 780
Hadith Gradingتحقیق (حسین سلیم أسد الدارانی):محمد بن إسحاق مدلس وقد عنعن ولكن الحديث صحيح، [مكتبه الشامله نمبر: 784]
Hadith Takhrijاس سند سے یہ روایت ضعیف ہے، لیکن دوسری سند سے حدیث صحیح متفق علیہ ہے۔ دیکھئے: [بخاري 286] ، [مسلم 305] ، [صحيح ابن حبان 1217] ، [البيهقى فى معرفة السنن والآثار 1517] و [المحلي 220/2]
Brief Explanation
(Commentary on Hadiths 778 to 780)
Therefore, whoever wishes to sleep in a state of major ritual impurity (janabah) should perform ablution (wudu). This is for the ease of the Ummah; he should sleep after performing ablution, but must perform the ritual bath (ghusl) before the prayer. Otherwise, if due to laziness or negligence he misses the prayer, he will be sinful.