Śatapatha Brāhmaṇa ("of a hundred paths") 2.1.2.4

2.1.2.4

atha yasmānna kṛttikāsvādadhīta | ṛkṣāṇāṃ ha vā etā agre patnya āsuḥ saptarṣīnu ha sma vai purarkṣā ityācakṣate tā mithunena vyārdhyantāmī hyuttarāhi saptarṣaya udyanti pura etā aśamiva vai tadyo mithunena vyṛddhaḥ sa nenmithunena vyṛdhyā iti tasmānna kṛttikāsvādadhīta

On the other hand (it is argued) why he should not set up the fires under the Krittikâs. Originally, namely, the latter were the wives of the Bears (riksha); for the seven Rishis were in former times called the Rikshas (bears). They were, however, precluded from intercourse (with their husbands), for the latter, the seven Rishis, rise in the north, and they (the Krittikâs) in the east. Now it is a misfortune for one to be precluded from intercourse (with his wife): he should therefore not set up his fires under the Krittikâs, lest he should thereby be precluded from intercourse.