حَدَّثَنِي يَحْيَى، عَنْ مَالِكٍ، عَنْ أَبِي الزِّنَادِ، عَنِ الأَعْرَجِ، عَنْ أَبِي هُرَيْرَةَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ ‏"‏ إِذَا اسْتَيْقَظَ أَحَدُكُمْ مِنْ نَوْمِهِ فَلْيَغْسِلْ يَدَهُ قَبْلَ أَنْ يُدْخِلَهَا فِي وَضُوئِهِ فَإِنَّ أَحَدَكُمْ لاَ يَدْرِي أَيْنَ بَاتَتْ يَدُهُ ‏"‏ ‏.‏

Yahya related to me from Malik from Abu'zZinad from al-Araj fromAbu Hurayra that the Messenger of Allah, may Allah bless him and granthim peace, said, "When you wake up from sleep to pray, wash your handsbefore you put them in the wudu water, for you do not know where yourhands have spent the night." Translation Not Available

Book reference: Muwatta Imam Malik Book 2 Hadith 38
Web reference: Muwatta Imam Malik Book 2 Hadith 9