Tafsir of As-Saffat 37:66

(Then they will be eating from it): This is a consequence derived from designating it as a fitnah—meaning an affliction and a torment for the wrongdoers. The feminine pronoun refers to the tree, and "from" (min) is either originative (ibtida'iyyah) or partitive (tab'idiyyah), with an implied noun—meaning from its fruit (tal'iha).

It is also said: "From" (min) is partitive, and the pronoun refers to the fruit (al-tal') itself; it is treated as feminine because it is annexed to a feminine noun, or because it is interpreted as the fruit (al-thamrah), or because it refers to the tree. Each of these interpretations is not without some distance.

(Then filling therefrom the bellies): This is due to the intensity of hunger, even if they loathe it, or because they are compelled to consume it.