Tafsir of Al-Mu'minoon 23:8

They are those who uphold them and safeguard them. The root of the word ra‘yun (observance/tending) refers to the guarding of animals, either by providing the sustenance that preserves their life or by repelling enemies from them; then, it was used to mean safeguarding in an absolute sense.

Al-amanat (trusts) is the plural of amanah. Originally, it is a verbal noun (masdar), but here it is intended to mean that which one is entrusted with—the objective essence, not the abstract meaning. As for its being pluralized, that does not negate this, for verbal nouns may be pluralized, as we mentioned not long ago. The same applies to the ‘ahd (covenant), which is a verbal noun intended to mean that which one has been covenanted upon.

According to the majority of exegetes, the verse is general, encompassing everything one is entrusted with and covenanted upon, whether from the perspective of Allah Almighty or from the perspective of people—such as religious obligations, deposited wealth, oaths, vows, contracts, and the like. Amanah was pluralized while ‘ahd was not, because trusts are very diverse and numerous for every legally responsible person (mukallaf) from the perspective of Allah, and hardly any such person is free of them, which is not the case for covenants.

Some exegetes permitted the view that it is specific to what they were entrusted with and covenanted upon by people, but that is not the preferred view. In my opinion, it is possible that "trusts" refers to what Allah Almighty has entrusted them with: their limbs and faculties, and that observing them means safeguarding them from being used in a manner contrary to His command, Majestic and Exalted is He. It is also possible that "covenant" refers to what Allah Almighty has taken from them in terms of what He has commanded them with in His Book and upon the tongue of His Messenger (peace be upon him), and that observing it means safeguarding it from being neglected, by performing it in the most perfect manner. Thus, guarding the trusts is like emptying [the soul of vices], and guarding the covenant is like adorning [it with virtues]. It is as if He, Majestic and Exalted, after mentioning their guarding of their chastity, mentioned their guarding of that which includes it and other things. It is permissible to make "trusts" general so that it includes wealth and the like, and it was pluralized due to the tangible and observable multiplicity within it; so ponder this.

Ibn Kathir and Abu ‘Amr, in one narration, read it as li-amanatihim (singular: "to their trust").