From Sahih Bukhari (Hadith 1276):
Narrated Khabbab:We emigrated with the Prophet (ﷺ) in Allah's cause, and so our reward was then surely incumbent on Allah. Some of us died and they did not take anything from their rewards in this world, and amongst them was Mus`ab bin `Umair; and the others were those who got their rewards. Mus`ab bin `Umair was martyred on the day of the Battle of Uhud and we could get nothing except his Burd to shroud him in. And when we covered his head his feet became bare and vice versa. So the Prophet (ﷺ) ordered us to cover his head only and to put idhkhir (a kind of shrub) over his feet
Reference: Bukhari 1276