Abu Hurayrah (may Allah be pleased with him) reported that the Prophet (may Allah's peace and blessings be upon him) said: "Do not envy one another, do not raise prices by overbidding against one another, do not hate one another, do not turn your backs on each other, and do not undercut one another in trade; but be, O slaves of Allah, as brothers. A Muslim is the brother of a Muslim; he does not wrong him, he does not fail him (when he needs him), he does not lie to him, and he does not show contempt for him. Piety lies here - and he pointed to his chest three times. It is enough evil for a Muslim to hold his Muslim brother in contempt. All of a Muslim is inviolable to another Muslim: his blood, his property, and his honor."
In this Hadīth, the Prophet (may Allah's peace and blessings be upon him) guides us to what is obligatory for us towards our fellow Muslims. We should love each other, be friendly with each other, deal with each other in a kind way that leads us to noble morals, keeps us away from evil morals, removes hatred to our fellow Muslims from our hearts, and makes our treatment of each other sublime and refined, free from jealousy, oppression, cheating and any other evils that may lead to harm or dissension. Harming a Muslim is prohibited, whether it is done through money, a transaction, the hand, or the tongue. All of the Muslim is inviolable to his fellow Muslim; his blood, his property, and his honor. Nobility and honor are acquired by virtue of piety alone.