俱舍論記 10.172

10.172

「又契經說至皆謂已生」者，又引經顯食唯有漏。部多、求生皆三有身，四食既能安住資益，明知有漏。無漏不然，為滅諸有，故非食體。

Regarding 'Furthermore, a sūtra says [...] all refer to those already born': This further cites a sūtra to show that food is solely sāsrava. 'Beings' and 'those seeking rebirth' are both bodies of the three existences; since the four foods can sustain and benefit them, it is clear that they are sāsrava. The anāsrava is not so, for it aims at the destruction of all existences, and is therefore not the substance of food.