Muhammad bin Sirin (may Allah have mercy on him) narrates that he learned the method of washing (the dead) from Umm Atiyyah (may Allah be pleased with her): she would wash twice with lote-tree leaves and the third time with water and camphor. And it is narrated from Abdullah bin Amr (may Allah be pleased with them both) that his father instructed him: O my son, when I die, wash me once with water. Ata' (may Allah have mercy on him) says that washing me once is sufficient. Umar bin Abd al-Aziz (may Allah have mercy on him) says that nothing is fixed in this. Ibrahim (may Allah have mercy on him) says that when lote-tree leaves and the like are not available, there is no harm. And the companions of Abdullah (may Allah be pleased with him) used to say that the deceased is to be washed once each time, with a single shroud, and istinja' is to be done once.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنائز / 6634