kiṃ ca yat saṅghātarūpaṃ tat pauruṣeyaṃ, yathā nāṭakākhyāyikādikathā, padasaṅghātaś ca veda iti svabhāvahetuḥ
Moreover, whatever has the form of a compilation is of human origin, like dramas, stories and such narratives, and the Veda is a compilation of words - this is a reason based on essential nature.