The Messenger of Allah (s) says:
“Among the best things about a man being Muslim is that he does not interfere in things with he is not concerned, so beware of this as you will not be excused it.”1
In this hadith, the Holy Prophet (s) forbids us from interfering in the affairs of people which have nothing to do with us and with which we have no connection.
For example, if you see two persons holding a private conversation, do not eavesdrop or try to join in. It maybe that they have certain confidences between them which they do not want others to be aware of or involved in.
If someone says something which has nothing to do with you, do not try to involve yourself in such a conversation, or speak as a representative for one who has not asked you. And if you find out something which does not concern you, do not use it to intervene.
For example, do not lend your friend's book to another person. It is not yours to do so, and if you do indeed you have interfered in another person's business.
For sure, the faithful with strong beliefs and good morals is not arrogant and never interferes in other's affairs.
If you do involve yourself, indeed you have committed a grave mistake against people and must correct yourself by apologizing because you have done harm to others in affairs that do not concern you. Among the best characteristics of the believer is not doing harm to anyone and in case of erring, one should repent and confess their fault.
A faithful differs from a hypocrite, who never admits his/her mistake nor apologizes for the harm he/she continually does against people.
Although it is among the believer's characteristics not to become involved in others' affairs and not to be officious, it is necessary to distinguish between interfering and intervening in the case of bidding what is right and forbidding what is wrong.
For instance, it we see a person committing a crime, or lying, stealing, or oppressing others, or deceiving or behaving in a vulgar manner, it is obligatory upon us to advise them of their wrong doing in order that they abstain from such misdeeds. Such intervention is not interfering but only doing one's moral duty as a true believer.
1. Surely, among the faithful's characteristics is not to interfere in the affairs of others.
2. The faithful neither hurts others nor causes them harm, and if he commits a mistake he apologizes.
3. The hypocrite only harms and hurts others and never apologizes to them.
There is no god but Allah and Muhammad is the Messenger of Allah.