Manava Dharmashastra 5.81

5.81

śrotriye tūpasaṃpanne trirātram aśucir bhavet
mātule pakṣiṇīṃ rātriṃ śiṣyartvigbāndhaveṣu ca //

For a Srotriya who resides with (him out of affection), a man shall be impure for three days; for a maternal uncle, a pupil, an officiating priest, or a maternal relative, for one night together with the preceding and following days.