Muwatta Malik · Hadith 38

وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ زَيْدِ بْنِ أَسْلَمَ، أَنَّ عُمَرَ بْنَ الْخَطَّابِ، قَالَ إِذَا نَامَ أَحَدُكُمْ مُضْطَجِعًا فَلْيَتَوَضَّأْ ‏.‏

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)

Gradings are classical jarḥ-wa-taʿdīl, name-matched to a rijāl index (not individually re-verified).