Agnipurana 158.16

158.16

maraṇādeva kartavyaṃ saṃyogo yasya nāgnibhiḥ
dāhādūrdhvamaśaucaṃ syādyasya vaitāniko vidhiḥ

[Impurity] is to be reckoned from death itself for one who has no connection with the [sacred] fires;
for one who follows the solemn rites of the Veda, ritual impurity begins after cremation.