Musannaf Ibn Abi Shayba 1:1118

1118. Abu Bakr narrated to us, he said: Abu al-Ahwas narrated to us, from ‘Ata’, from Zadhan, from ‘Ali, who said: If a man becomes in a state of major ritual impurity (junub) in a desert land and he has a little water with him, he should prioritize himself with the water and perform tayammum with the soil.