Shankhayanagrihyasutra 2.12.7

2.12.7

: trirātram samid ādhānam bhikṣā caraṇam adhaḥ śayyām guru śuśrūṣām ca ākurvan.(?).vāg yato apramatto araṇye deva kule agni hotre vo apavasasva iti /

Here some (teachers) prescribe the same observances only for one night, during which he is to stand.