Wonder why whenever we go to attend a funeral, we wash our hands right away? I researched about this and this is what I’ve got.
One of the reasons about hand washing is partly being a matter of practical hygiene if people were helping to carry the casket, or if there is a health threat as exemplified by an epidemic like the Cholera (see article here). A more symbolic reason would be about the living significant others’ way of washing away the associations of death as their loved one departs them to the final resting place.
A controversial version also exists, and it dates back to the New Testament when Pontius Pilate was washing his hands over the death of Jesus, and a text in Deuteronomy 21.7 about a scenario wherein a man was found dead with no one to know the murderers identity, and the elders made a ritual including washing of the hands, to declare their innocence about the crime.