It is sunnah (advisable) to perform wudhu (ablution) before going to sleep at night. It cleanses your body, so that you sleep at best condition. Also you get merit from Allah even when you are sleeping.
A hadith from Ibn Umar (may Allah blesses him), that the Messenger of Allah ﷺ says,
طَهِّرُوا هَذِهِ الأَجْسَادَ طَهَّرَكُمُ اللَّهُ مَا مِنْ عَبْدٍ بَاتَ طَاهِرًا إِلا بَاتَ فِي شِعَارِهِ مَلَكٌ كُلَّمَا تَقَلَّبَ مِنَ اللَّيْلِ سَاعَةً قَالَ الْمَلَكُ اللَّهُمَّ اغْفِرْ لِعَبْدِكَ كَمَا بَاتَ طَاهِرًا
“Purify these bodies of yours, that Allah may purify you. No servant retires for the night in a state of purity but that an angel resides with him in his bed. Every time he turns about for an hour, the angel says: O Allah, forgive your servant, as he has retired in a state of purity” [al-Mu’jam al-Kabir, classed as hasan by al-Albani].
It is sunnah to do the wudhu (ablution) before you sleep. Make it a good habit of yours.
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