Mimamsasutra 42.2.23-4

42.2.23-4

ubhayadharmasāhityaṃ viruḍhḍham| ’uccairgeyam| balavadgeyam’ iti bṛhaḍhḍharmāḥ| ’noccairgeyam| na balavadveyam’ iti rathaṃtaradharmāḥ| tasmāt- ubhayordharmā vyavatiṣṭhante ||

Combining the ritual details of both is contradictory. 'It should be chanted loudly; it should be chanted strongly' are the ritual details of the Bṛhat. 'It should not be chanted loudly; it should not be chanted strongly' are the ritual details of the Rathaṃtara. Therefore, the ritual details of both are distributed.