Yahya related to me from Malik from Abu'zZinad from al-Araj from Abu Hurayra that the Messenger of Allah ﷺ said, "When you wake up from sleep to pray, wash your hands before you put them in the wudu water, for you do not know where your hands have spent the night."  

أَنَّ رَسُولَ اللَّهِ ﷺ 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 Zayd ibn Aslam that Umar ibn al-Khattab said, "If you fall asleep Iying down you must do wudu ( before you pray) . "  

قَالَ إِذَا نَامَ أَحَدُكُمْ مُضْطَجِعًا فَلْيَتَوَضَّأْ  

Yahya related to me from Malik from Zayd ibn Aslam that the ayat "You who believe! When you rise for prayer wash your faces, and your arms to the elbows, and wipe over your heads and your feet up to the ankles," refers to rising from bed, meaning sleep. Yahya said that Malik said, "The situation with us is that one does not have to do wudu for a nose-bleed, or for blood, or for pus issuing from the body. One only has to do wudu for impurities which issue from the genitals or the anus, or for sleep."  

أَنَّ تَفْسِيرَ هَذِهِ الآيَةِ يَا أَيُّهَا الَّذِينَ آمَنُوا إِذَا قُمْتُمْ إِلَى الصَّلاَةِ فَاغْسِلُوا وُجُوهَكُمْ وَأَيْدِيَكُمْ إِلَى الْمَرَافِقِ وَامْسَحُوا بِرُءُوسِكُمْ وَأَرْجُلَكُمْ إِلَى الْكَعْبَيْنِ أَنَّ ذَلِكَ إِذَا قُمْتُمْ مِنَ الْمَضَاجِعِ يَعْنِي النَّوْمَ قَالَ يَحْيَى قَالَ مَالِكٌ الأَمْرُ عِنْدَنَا أَنَّهُ لاَ يَتَوَضَّأُ مِنْ رُعَافٍ وَلاَ مِنْ دَمٍ وَلاَ مِنْ قَيْحٍ يَسِيلُ مِنَ الْجَسَدِ وَلاَ يَتَوَضَّأُ إِلاَّ مِنْ حَدَثٍ يَخْرُجُ مِنْ ذَكَرٍ أَوْ دُبُرٍ أَوْ نَوْمٍ  

Yahya related to me from Malik from Nafithat Ibn Umar used to sleep sitting and then would pray without doing wudu.  

أَنَّ ابْنَ عُمَرَ كَانَ يَنَامُ جَالِسًا ثُمَّ يُصَلِّي وَلاَ يَتَوَضَّأُ