Fiqh-us-Sunnah Volume 1, Purification and Prayer, Fiqh 1.056A.

According to many scholars, performing ghusl is also preferred for one who has washed a corpse. Abu Hurariah reported that the Prophet, upon whom be peace, said, “Whoever has washed a corpse must perform ghusl, and whoever carried him must perform ablution.” (Related by Ahmad, Abu Dawud, at-Tirmizhi, an-Nasa’i, Ibn Majah and others.) However, there is some criticism of this hadith. ‘Ali ibn al-Madani, Ahmad, Ibn al-Munzhir, ar-Rafi’ and others say, “The hadith scholars did not classify anything on this topic as authentic.” But Ibn Hajr quotes at-Tirmizhi and Ibn Hibban: “At-Tirmizhi called it hassan and Ibn Hibban called it sahih. And, due to its numerous chains, it is most likely hassan. An-Nawawi strongly refutes what at-Tirmizhi said.” Says azh-Zhahabi, “The chains of this hadith are stronger than a number of chains of the hadith that the jurists argue by.” The order in the hadith implies preference, based on what has been related by ‘Umar, who said, “We used to wash the dead. Some of us would perform ghusl and some would not.” (Related by al-Khateeb with a sahih chain.) When ‘Asma bint Umaish washed the body of her deceased husband, Abu Bakr as-Siddiq, she asked if there were any among the emigrants present, and said, “This day is extremely cold and I am fasting. Do I have to make ghusl?” They said, “No.” (Related by Malik.)