It is narrated from Ata that Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) was asked: Is a ritual bath required of the one who washes a deceased person? He said: Have you declared your companion impure? Ablution is sufficient for it.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 1459