Manava Dharmashastra 5.67

5.67

nṛṇām akṛtacūḍānāṃ viśuddhir naiśikī smṛtā
nirvṛtta tu trirātrāc chuddhir iṣyate //

(On the death) of children whose tonsure (Kudakarman) has not been performed, the (Sapindas) are declared to become pure in one (day and) night; (on the death) of those who have received the tonsure (but not the initiation, the law) ordains (that) the purification (takes place) after three days.