Shatapatha Brahmana 13.1.2.1

13.1.2.1

vyṛddhamu vā etadyajñasya yadayajuṣkeṇa kriyata imāmagṛbhṇanraśanāmṛtasyetyaśvābhidhānīmādatte yajuṣkṛtyai yajñasya samṛddhyai dvādaśāratnirbhavati dvādaśa māsāḥ saṃvatsaraḥ saṃvatsarameva yajñamāpnoti

Now, unsuccessful in the sacrifice, assuredly, is what is performed without a formula. (With Vâg. S. XXII, 2,) 'This rope did they take, at the first age of the truth, [the sages, at the rites: it hath been with us at this Soma-sacrifice, declaring the course in the gaining of the truth],' he takes the halter of the horse in order to supply a formula for the success of the sacrifice. It (the rope) is twelve cubits long,--twelve months make a year: it is the year, the sacrifice, he secures.