Sunan an-Nasa'i, Hadith 5323 ⓘ
It was narrated that Samurah said: "The Messenger of Allah [SAW] said: 'You should wear white garments; dress your living ones in them, and shroud your dead in them, for they are among the best of your garments.'"
أَخْبَرَنَا قُتَيْبَةُ، قَالَ حَدَّثَنَا حَمَّادٌ، عَنْ أَيُّوبَ، عَنْ أَبِي قِلاَبَةَ، عَنْ سَمُرَةَ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " عَلَيْكُمْ بِالْبَيَاضِ مِنَ الثِّيَابِ فَلْيَلْبَسْهَا أَحْيَاؤُكُمْ وَكَفِّنُوا فِيهَا مَوْتَاكُمْ فَإِنَّهَا مِنْ خَيْرِ ثِيَابِكُمْ " .
also referenced under: Book 48, Hadith 284 (In-Book) & Volume 6, Book 48, Hadith 5325 (DarusSalam)