Tafsir of Al-Adiyat 100:10

(And what is in the breasts is gathered/brought forth) means that which is in the hearts, of resolute intentions, is collected and manifested, like the manifestation of the kernel from the husk. It is brought together, or its good is distinguished from its evil. The verb hussila (to gather/bring forth) is used here in the sense of "distinguishing/separating," as mentioned in Al-Bahr. The root of tahsil (attainment/gathering) is the extraction of the kernel from the husk, like extracting gold from mineral ore or grain from chaff.

What is in the hearts is specified because it is the foundation for the actions of the limbs; this is why [it is said that] "actions are by intentions," and why the first of thoughts is the last of actions. Thus, everything that is done is subordinate to it, and [the phrase] indicates everything [of one's deeds], both explicitly and implicitly.

Ibn Ya‘mar, Nasr ibn ‘Asim, and Muhammad ibn Abi Ma‘dan recited it as hassala (he gathered/brought forth), in the active voice, with the pronoun referring to Him, the Exalted and Majestic. Ibn Ya‘mar and Nasr also recited it as hasala (he gathered/brought forth), in the active voice, with a light (un-doubled) sad; in this case, the pronoun refers to Him, the Exalted.