Vasiṣṭha's teaching (Mahārāmāyaṇa) 6.28.35

6.28.35

tathaiva dṛśyate dehastathā''kṛtyudayena saḥ .
pauruṣeṇa prayatnena saṃkalpo hyayameva cit .. 35

35. [Sanskrit available] The body shows itself in the form as it is shaped by the prior acts of a person, and is also convertible to the intellect by the manly exertions of some: (whose corporeal bodies may become intellectual beings, as some persons have mere brutal, while others are highly intellectual).