Vayupurana 2.17.62

Vāyupurāṇa 2.17.62

śrāddhaṃ dattvā ca bhuktvā ca maithunaṃ yo niṣevate.
pitarastasya taṃ māsaṃ retaḥsthā nātra saṃśayaḥ .. 17.60 ..