Manava Dharmashastra 5.62

5.62

mātāpitros tu sūtakam
sūtakaṃ mātur eva syād upaspṛśya pitā śuciḥ //

(Or while) the impurity on account of a death is common to all (Sapindas), that caused by a birth (falls) on the parents alone; (or) it shall fall on the mother alone, and the father shall become pure by bathing;