Kauṣītaki (Śāṅkhāyana) Brāhmaṇa 4.7.14

4.7.14

imān eva tal lokān āpnoti / (Vikṛti iṣṭayah)

desiring heaven sacrifice. In that he puts on a black antelope’s skin, and the black antelope’s skin is the holy power, verily thus he unites the sacrifice with holy power. There are three oblations; these worlds are three; verily thus he obtains these worlds.