Is It Necessary to Make Ghusl after Washing the Dead?
Question

Do the people that bathe the dead have to change clothes or take a bath before praying janazah?
Praise be to Allah.The correct scholarly view is that doing Ghusl after washing the deceased is recommended, but it is not obligatory. 
This is the view of Ibn `Abbas, Ibn `Umar, `Aishah, Al-Hasan Al-Basri, Ibrahim An-Nakha`i, Ash-Shafi`i, Ahmad, Ishaq, Abu Thawr, Ibn Al-Mundhir and others, and it is also the view regarded as most correct by Ibn Qudamah. (See Sunan At-Tirmidhi, 3/318; Al-Mughni, 1/134) 
Shaykh Al-Albani (may Allah have mercy on him) said: 
“It is recommended for the one who washes the deceased to do Ghusl , because the Prophet (peace and blessings of Allah be upon him) said: “Whoever washes the dead, let him do Ghusl, and whoever carries him, let him do Wudu.” (Narrated by Abu Dawud, 2/62-63; At-Tirmidhi, 2/132. Some of its isnads (chains of narration) are good, and some are authentic according to the conditions of Muslim. Ibn Al-Qayyim quoted eleven isnads for it in Tahdhib As-Sunan, then he said: These isnads indicate that the Hadith is mahfudh (preserved). 
I say: it was classed as authentic by Ibn Al-Qattan, and by Ibn Hazm in Al-Muhalla, 1/250 and 2/23-25, and by Al-Hafidh in At-Talkhis, 2/134 (Muniriyyah edition). And he said, at the very least it is good. 
The apparent meaning of the Hadith indicates that it is a must, but we did not suggest that it is a must because of two mawquf hadiths that are to be taken as marfu`: 

From Ibn `Abbas: “When you wash your dead you do not have to do Ghusl afterwards, for your dead are not impure. It is sufficient for you to wash your hands.” (Narrated by Al-Hakim, 1/386; Al-Bayhaqi, 3/398)

It seems to me most likely that this Hadith is mawquf, as I have explained in Ad-Da`ifah, 6304. 

Ibn `Umar (may Allah be pleased with him) said: “We used to wash the deceased, and some of us would do Ghusl afterwards and others would not.” (Narrated by Ad-Daraqutni, 191; Al-Khatib in his Tarikh, 5/424, with an authentic isnad as Al-Hafidh said. This was also referred to by Imam Ahmad. Al-Khatib narrated from him that he urged his son to write down this Hadith.” (Ahkam Al-Jana’iz, 71. 72) 

This is what is regarded as most likely to be correct by the Standing Committee (1/318), and by Shaykh Ibn `Uthaymin in Ash-Sharh Al-Mumti`, 1/295 
With regard to washing the clothes, there is no basis for doing so in the Sunnah, and it is neither obligatory nor recommended.
For more details, please see the following answers: 174754 , 14016 , 155045 , 39288 , 105360 , and 194752 .
And Allah knows best.