Praise be to Allah, Who brought the hearts of His pious servants together, so that, by His favor, they became brethren. May Allah’s peace and blessings be upon the bearer of glad tidings and warner, with whom Allah has brought the hearts of the believers together, and for those who follow him and obey him, He assured forgiveness of sins.

The Muslims are brethren. Allah, the Almighty, has linked their hearts with the bond of Tawheed (monotheism), by virtue of which Allah, the Almighty, called them Muslims.

Brothers love, rather than hate each other. Their faith forbids them from hatred, which is prompted by whims, enemies, and evil souls which are inclined to evil. However, if dislike is for the sake of Allah, it is required and approved. A Muslim will not attain Allah’s guardianship (walayah) unless he likes, dislikes, keeps loyal, or shows hostility for Allah’s sake. The Prophet () said: “Do not hate one another ” meaning: Do not do things that bring about hatred among you. Love makes some people happy, and hatred makes others miserable.

Hatred between praise and dispraise:

Ibn Rajab commented on the Prophet’s () saying “Do not hate one another” and said: “He forbade Muslims to hate each other for anything other than Allah’s sake and not in response to the evil prompts of the souls. Allah has made Muslims brothers, and it is becoming of brothers to love each other rather than hate each other.

The Prophet () said: “By Him in Whose Hand my soul is! You will not enter Jannah until you believe, and you shall not believe until you love one another. Shall I not tell you something which, if you do it, you will love one another? Spread (the greeting of) Salam amongst yourselves.” (Narrated by Muslim)

Allah has forbidden the believers to do anything that would cause enmity and hatred among them; He, the Almighty, said: “Satan only wants to cause between you animosity and hatred through intoxicants and gambling and to avert you from the remembrance of Allah and from prayer. So will you not desist?” [Quran 5: 91]

He reminded His servants of the favor He conferred upon them by bringing their hearts together. He, the Almighty, said: “And remember the favor of Allah upon you – when you were enemies and He brought your hearts together and you became, by His favor, brothers.” [Quran 3: 103] “It is He who supported you with His help and with the believers and brought together their hearts. If you had spent all that is in the earth, you could not have brought their hearts together; but Allah brought them together.” [Quran 8: 62-63] For this very reason, it is forbidden to engage in tale-bearing, due to the enmity and hatred it sows among people.

As for hatred for the sake of Allah, it is one of the firmest bonds of faith and is not included in this prohibition. If a man observes that his brother is committing an evil and hates him for that evil, he will be rewarded even if the former is (inwardly) excused. ‘Umar said: “We used to know you in the time of the Messenger () while revelation was descending, and Allah was telling us about you. But now the Messenger has died, and the revelation has ceased, so we judge you according to our knowledge. Whoever among you shows us good, we will trust him and love him for it, and whoever among you shows us evil, we will think bad of him and hate him for it. Allah, the Almighty, will hold you accountable for your inner secrets.” Al-Rabi' ibn Khuthaym said, "If you see a man who publicly shows good deeds and secretly does evil, you should love him [for what you know] and Allah will reward you for your loving of good. If you see a man who openly shows evil and hides his good deeds, then hate him [for what you know] and Allah will reward you for your hate of the evil.”

When the differences of people on the issues of religion increased and their mutual divisions increased, their mutual hatred and abuse increased. Each one of them apparently claimed that his hatred was for the sake of Allah.  He may sometimes be really excused, but at other times he may not, rather he may in fact be following his own whims and falling short in investigating enough to have real knowledge of that for which he hates the other person. Also, a great deal of hatred comes about because of disagreeing with someone whom people follow, and his followers believe that he only says the truth. This belief is absolutely wrong. If it is meant that he [the one they follow] only says the truth about issue about which others may differ with him, then this belief may sometimes be right and sometimes may be wrong. It may also be that the only thing which inclines one to that hatred is simply one’s own whims or close companionship or habit, all of which detract from this hatred being for the sake of Allah. It is obligatory for the believer to be truthful to himself and to guard himself against this to the furthest possible limit.” (End quote)

The disbelievers hate the believers:

Allah, the Almighty, said: “O you who have believed, do not take as intimates those other than yourselves [i.e., believers], for they will not spare you [any] ruin. They wish you would have hardship. Hatred has already appeared from their mouths, and what their breasts conceal is greater. We have certainly made clear to you the signs, if you will use reason. Here you are loving them but they are not loving you, while you believe in the Scripture – all of it. And when they meet you, they say, "We believe." But when they are alone, they bite their fingertips at you in rage. Say, "Die in your rage. Indeed, Allah is Knowing of that within the breasts."” [Quran 3: 118-119]

Ibn Kathir, may Allah have mercy on him, commented on Allah’s saying “Hatred has already appeared from their mouths” and said: “Enmity appears on their faces and in their slips of the tongue as well as the enmity they have against Islam and its people in their hearts. Since this fact is apparent to every person who has sound comprehension.”

The Prophet () forbids mutual hatred:

The Messenger of Allah () forbade mutual hatred among believers in many Hadiths, including the following:

Abu Hurayrah (may Allah be pleased with him) reported that the Messenger of Allah () said, "Beware of suspicion. Suspicion is the most untrue speech. Do not eavesdrop and do not spy. Do not envy each other, do not hate each other and do not shun each other. Be slaves of Allah, brothers."

Anas ibn Malik (may Allah be pleased with him) said: The Messenger of Allah () said, "Do not nurse hatred towards one another, do not be jealous of one another, and do not desert (stop talking to) one another. Rather, become as fellow brothers and slaves of Allah. It is not lawful for a Muslim to stop talking to his brother (Muslim) for more than three days."

Reprehensible competing for this world leads to hatred:

‘Abdullah ibn `Amr ibn al-`Aas reported that Allah's Messenger ( ) said: “How would you be, O people, when Persia and Rome would be conquered for you?” ‘Abdur-Rahman ibn ‘Awf said: We would say as Allah has commanded us (we would express our gratitude to Allah). Thereupon Allah's Messenger () said: “Nothing else besides it? You would (in fact) vie with one another, then you would feel jealous, then your relations would be estranged and then you will bear enmity against one another, or something to the same effect.”

Abu Sinan Al-Dua’li narrated that he entered upon ‘Umar ibn Al-Khattab (may Allah be pleased with him) and he had a group of the early Immigrants. 'Umar sent for a basket that had been brought to him from Iraq, in which there was a ring. One of his sons took it (the ring) and put it in his mouth. ‘Umar took it from him, then 'Umar wept and those who were with him said: Why are you weeping when Allah has granted victory to you and caused you to prevail over your enemies and granted you joy? 'Umar said: I heard the Messenger of Allah () say: “Accumulation of worldly luxuries does not become available to any people but Allah (may He be Glorified and Exalted) stirs up among them enmity and hatred until the Day of Resurrection ” and that concerns me.

It was narrated that Abu Hurayrah (may Allah be pleased with him), said: I heard the Messenger of Allah () say: “My Ummah will be affected by the disease of nations.” They said: O Messenger of Allah, what is the disease of nations? He said: “Arrogance, pride, multiplication of wealth, quarreling over this world, hatred and envy until the transgression takes place.”

It was narrated on the authority Az-Zubayr ibn Al-‘Awwam (may Allah be pleased with him) that the Prophet () said: “There has come to you the disease of the nations before you, jealousy and hatred. Hatred is the ‘shaver’ (destroyer). I don’t say that it shaves hair, but it shaves (destroys) religious commitment. By the One in Whose Hand the soul of Muhammad is, you will not believe until you love one another. Shall I not tell you something which, if you do it, you will love one another? Spread (the greeting of) Salam amongst yourselves.”