Musab bin Umayr was killed on the day of Uhud, and he had nothing but a striped cloak. When we covered his head with it, his feet were exposed, and when we covered his feet, his head was exposed. So the Messenger of Allah ﷺ said, "Cover his head with it, and place some idhkhir grass over his feet."
حدثنا محمد بن كثير أخبرنا سفيان عن الأعمش عن أبي وائل
مصعب بن عمير قتل يوم أحد ولم تكن له إلا نمرة كنا إذا غطينا بها رأسه خرجت رجلاه وإذا غطينا رجليه خرج رأسه فقال رسول الله ﷺ غطوا بها رأسه واجعلوا على رجليه من الإذخر
Narrated by Muslim, in the Book of Funerals, chapter on the shroud of the deceased, hadith no. 940, from the hadith of Sufyan and so on, hadith no. 1276, from the hadith of, and Bukhari, in the Book of Funerals, chapter "When he finds no shroud except what covers his head," from Amash, with this wording.