Kauṣītaki (Śāṅkhāyana) Brāhmaṇa 6.p38

6.p38

vii. 7. Thus did the gods discern by means of the introductory sacrifice the world of heaven; verily thus also does the sacrificer by the introductory rite discern the world of heaven. The introductory and concluding sacrifice should be alike. The sacrifice is a chariot of the gods; the introductory and concluding sacrifices are the two sides of it; he who makes them alike, just as one can perform a journey as desired by driving on in a chariot with two sides, so safely he attains the world of heaven. He who makes them unlike, just as one cannot perform a journey as desired by driving on in a chariot with one side only, so he does not safely attain the world of heaven. Therefore the introductory and the concluding sacrifices should be alike, the introductory ending with the Çaṃyuvāka, and the concluding sacrifice ending with the Çaṃyuvāka.