Brahma Sutras
ॐ सर्वापेक्षा च यज्ञादिश्रुतेः अश्ववत् ॐ ॥ ३-४-२६॥
On the strength of the Upanishadic sanction of sacrifices etc., all religious activities as well are necessary. This is the same as in the case of a horse (in matters of its adequacy).
english translation
OM sarvApekSA ca yajJAdizruteH azvavat OM ॥ 3-4-26॥
hk transliteration by Sanscript