Kautilya's Arthashastra 3.1.15

3.1.15

sve sve tu varge deśe kāle ca svakaraṇakṛtāḥ sampūrṇācārāḥ śuddhadeśā dṛṣṭarūpalakṣaṇapramāṇaguṇāḥ sarvavyavahārāḥ sidhyeyuḥ //

But such agreements as are entered into in person by any one with others of his own community in suitable place and time are valid provided the circumstances, the nature, the description, and the qualities of the case are credible.