Visuddhimagga XI-38

Iti vīsatiyā ākārehi pathavīdhātu, dvādasahi āpodhātu, catūhi tejodhātu, chahi vāyodhātūti dvācattālīsāya ākārehi catasso dhātuyo vitthāritā hontīti ayaṃ tāvettha pāḷivaṇṇanā.

如是详述四界的四十二种行相，即在地界中有二十种，水界中十二种，火界中四种，风界中六种。这是对经文的解释。

Ñ(XI,38): So the four elements have been detailed in forty-two aspects, that is to say, the earth element in twenty aspects, the water element in twelve, the fire element in four, and the air element in six. This, firstly, is the commentary on the texts here.