Agnipurana 252.61

252.61

asambaddhakṛtaś caiva vyavahāro na siddhyati /
pranaṣṭādhiśataṃ deyaṃ nṛpeṇa dhanine dhanaṃ //

And a legal transaction made by an unauthorized person does not succeed. / The king should return lost property to the owner after showing it for a hundred days;