Skandapurana 7.13.p41

7.13.p41

tato vimokṣyate devaḥ16 sanaro brahmavadhyayā .
tamevaṃvādinaṃ devāḥ praṇamya śirasā tadā .
ūcuḥ prāñjalayaḥ sarve kintapaḥ karma śādhi naḥ . .27. .
brahmovāca
japadhvaṃ prayatāḥ sarve vāyubhakṣā jitendriyāḥ .
rudrāṇāṃ hṛdayaṃ samyak tato yogamavāpsyatha . .28 ..

Then the god, along with Nara, will be freed from the [sin of] brahmin-slaughter."
Bowing their heads to him as he spoke thus,
all the gods, with folded hands, said:
"Instruct us: what austerity, what rite [should we perform]?" // 27
Brahmā said:
"Disciplined, feeding on air, with senses conquered,
all of you properly chant the Rudrahṛdaya; thence you will attain yoga." // 28