The messenger of Allāh (sallallāhu alaihi wa salam) said,
‘Whomsoever performs ghusl for a (deceased) Muslim and conceals (his affairs), he will be forgiven 40 times…”
To attain this reward there are two conditions
1. That he conceal the dead person, i.e. he does not talk or disclose that which he has seen from disliked/unpleasant affairs (related to the deceased).
2. That he hopes and desires by way of washing the dead Muslim, the Face of Allāh, not seeking a reward or thanks or anything from the affairs of the worldly life.
Ahkhaam Al-Janaaiz Shaykh Albaani pg 69.
Hadeeth is Saheeh upon the conditions of Muslim