The Quran says in Verse 58 of Surah An-Nisa:
“Allah orders you all to hand back trusts to their owners, and when you judge between people you judge with justice. Indeed, the best is the exhortation with which Allah exhorts you. Allah is the Hearer, the Seer.”
The two commandments in this verse are written in our hearts with golden ink of Fitrat (nature). There is no one unaware of the fact that trusts must be handed back to their owners and that when judging among people, one must forget about personal desires or interests and judge with justice.
The evidence showing that these two commandments are based on Fitrat is that if you tell anyone they have betrayed the trusts of others, he will either deny it or feel ashamed of it.
Another sign for this is that in all cultures and in all nations, there are proverbs and sayings that recommend handing back trust to its owners.
So this verse needs no interpretation. One should just set aside all pretexts and act the right way, that is, judge justly when judging among people and return that which has been entrusted to you to the rightful owners.
It has been narrated from Imam Sajjad (AS) who said, “If the killer of my father deposited with me the sword with which he killed him, I would give it to him.”
As for judging with justice, it should be noted that being just in judgment is the duty of all people, but should be taken into account even more by those in power, including kings and rulers. It has been said that there is no act of worship attracting more thawab (rewards) than ruling with justice,
God says at the end of the verse: “God's advice is the most noble.” It shows that one of the most important divine pieces of advice is one that calls for justice and for returning what has been entrusted to you.
It is most important when it comes to the divine trust given to us, which is our Fitrat and heart that should be kept away from conceit and arrogance and be filled with moral virtues.