The following Verse:-- "If a guardian is well-off, let him claim no remuneration (i.e. wages), but if he is poor, let him have for himself what is just and reasonable." (4.6) was revealed in connection with the guardian of an orphan, and it means that if he is poor he can have for himself (from the orphan's wealth) what is just and reasonable according to the orphan's share of the inheritance.
Sahih al-Bukhari Book 55, Hadith 28
← Previous Hadith In the lifetime of Allah's Messenger (ﷺ) , `Umar gave in charity some of his property, a garden of date-palms called Thamgh. `Umar said, "O Allah's Messenger (ﷺ)! I have some property which I prize highly and I want to give it in charity." The Prophet; said, "Give it in charity (i.e. as an endowment) with its land and trees on the condition that the land and trees will neither be sold nor given as a present, nor bequeathed, but the fruits are to be spent in charity." So `Umar gave it in charity, and it was for Allah's Cause, the emancipation of slaves, for the poor, for guests, for travelers, and for kinsmen. The person acting as its administrator could eat from it reasonably and fairly, and could let a friend of his eat from it provided he had no intention of becoming wealthy by its means.

Sahih al-Bukhari Book 55, Hadith 27 Next Hadith → The Prophet (ﷺ) said, "Avoid the seven great destructive sins." The people enquire, "O Allah's Messenger (ﷺ)! What are they? "He said, "To join others in worship along with Allah, to practice sorcery, to kill the life which Allah has forbidden except for a just cause, (according to Islamic law), to eat up Riba (usury), to eat up an orphan's wealth, to give back to the enemy and fleeing from the battlefield at the time of fighting, and to accuse, chaste women, who never even think of anything touching chastity and are good believers.

Sahih al-Bukhari Book 55, Hadith 29