Skandapurana 5.8.105

5.8.105

paraṃ tasya vadhājjātā brahmahatyā sugarhitā ..
tava śakra na tenādya spṛśāmo'spṛśyatāṃ gatam .. 105 ..

However, from his slaying, the highly reprehensible murder of a brahmin has arisen
for you, O Śakra; therefore today we do not touch [you, who have] become untouchable. 105