What are the rights of a Muslim upon another Muslim?
The hadeeth on the rights of a Muslim upon another Muslim was reported by Imam Muslim.
Abu Huraira reported Allah's Messenger (ﷺ) as saying: Six are the rights of a Muslim over another Muslim. It was said to him: Allah's Messenger (ﷺ), what are these? Thereupon he (ﷺ) said:
"When you meet him, offer him greetings; when he invites you to a feast accept it, when he seeks your advice, advise him, and when he sneezes and praises Allah, then pray for mercy upon him; and when he becomes ill, visit him; and when he dies follow him (his funeral)." 
Whoever establishes these six rights in dealing with the Muslims, then his establishing things other than them (from the obligations) are even more important (or necessary), and his doing these things results in him fulfilling these obligations and rights, which contain an abundance of good and tremendous reward from Allah.
Let us look at these rights, one by one:
The First Right:
"When you meet him, give him the greeting of peace."
Verily the greeting of peace is a cause of love, which results in producing faith (Al-Emaan), which results in the person entering Paradise. This is as the Prophet (ﷺ) said,
"By the One in Whose Hand is my soul, you all will not enter Paradise until you believe, and you will not believe until you love each other. Shall I not direct you to something that if you do, you will love each other? Spread the greeting of peace amongst yourselves." 
The greeting of peace is from the virtuous characteristics of Islam, for verily each of the two people who meet each other supplicates for the other for safety from evils, to be granted mercy and blessing that brings about every good. What follows this is a cheerful face and appropriate words of greeting which result in unity and love, and it removes feelings of estrangement and cold disassociation. Thus, giving the greeting of peace is the right of the Muslim, and it is obligatory upon the person who is greeted to return the greeting with a similar greeting or one that is better than it as mentioned in Qur’an,
“And when you are greeted with a greeting, greet [in return] with one better than it or [at least] return it [in a like manner]...”
“The best of the people are those who start the greeting of peace first.”
The Second Right:
"When he invites you to a feast, respond to his invitation."
This means that when he invites you with an invitation to some food and drink, fulfil the request of your brother who has drawn near you and honoured you with the invitation. Respond to his invitation (i.e., accept it), unless you have an excuse.
The Third Right:
His statement, "And when he seeks your advice, advise him" means that if he seeks consultation with you regarding some action, as to whether he should do it or not, then advise him with that which you would like for yourself. Thus, if the action is something that is beneficial in all aspects, then encourage him to do that, and if it is something harmful, then warn him against it. If the action contains both benefit and harm, then explain that to him and weigh the benefits against the harms. Likewise, if he consults you concerning some dealing among the people, or whether he should marry a woman off to someone, or whether he should marry someone, then extend your pure and sincere advice to him, and deal with him from the view point of what you would do for you own self. Avoid deceiving him in any of these things. Verily whoever deceives the Muslims, then he is not of them, and indeed he has left off the obligation of being sincere and advising. This sincerity and advising is absolutely obligatory, however it becomes more emphasized when the person seeks your advice and he requests from you that you give him a beneficial opinion. For this reason the Prophet (ﷺ) said,
"The religion is sincerity” 
The Fourth Right:
"And when he sneezes and praises Allah, then pray for mercy upon him."
This is due to the fact that sneezing is a favor from Allah, in the expelling of this congested air that is blocked in certain parts of the body of the human being. Allah makes it easy for this air to have a passage out where it can exit, and thus the sneezing person feels relief. Thus, the Prophet (ﷺ) legislated that the person praise Allah for this favor, and he legislated for his (Muslim) brother to say to him, "May Allah have mercy upon you." He also commanded the person who sneezed to answer his (Muslim) brother by saying to him,
"May Allah guide you and set right your affairs." 
Therefore, whoever does not praise Allah does not deserve for others to pray for mercy upon him, and in this case he cannot blame anyone except himself. For, he is the one who has caused himself to lose the two blessings: the blessing of praising Allah, and the blessing of his brother's supplication for him that is a result of the praising.
The Fifth Right:
"And when he becomes ill, visit him."
Visiting the sick is from the rights of the Muslim, especially for the person who has a highly stressed and emphasized right upon you, like the relative, the friend, and so forth. It is from the best of the righteous deeds.
Ali Ibn Abi Taalib related that he heard the Messenger of Allah (ﷺ) say:
‘If a man calls on his sick Muslim brother, it is as if he walks reaping the fruits of Paradise until he sits, and when he sits he is showered in mercy, and if this was in the morning, seventy thousand angels send prayers upon him until the evening, and if this was in the evening, seventy thousand angels send prayers upon him until the morning” 
It is desired for the person who visits the sick to supplicate for him to be cured and to make him feel at ease. He should ease his worries by giving him glad tidings of well-being and recovery (i.e. be positive). He should remind him of repentance and turning to Allah, and give him beneficial admonition. He should not sit with him too long (i.e. over staying), rather he should only sit with him long enough to fulfil the right of visiting, unless the sick person is positively affected by many people coming in to see him and many people coming to sit with him. Thus, for each situation there is a different statement (i.e. advice on how to deal with it).
The Sixth Right:
"And if he dies, follow him (his funeral)."
“Whoever follows the funeral until the deceased's body is prayed over, then he will receive a Qeeraat of reward. A Qeeraat is an amount equivalent to the size of the Mountain of Uhud in Madinah. If he follows the funeral procession until the body is buried, then he will receive two Qeeraats of reward.” 
Following the funeral procession contains (fulfilment of) a right for Allah, a right for the deceased, and a right for the living relatives of the deceased.
 [Sahih al-Muslim, Hadith 4117]
 [Sahih Muslim; Jami` at-Tirmidhi 2688]
 [Qur’an, 4:86]
 [Sahih al-Bukari]
 [Sahih Muslim, 55]
 [Sahih al-Bukhari; Sunan Abi Dawud 5033]
 [at-Tirmidhi, 967; Sunan Ibn Majah, Book 6, Hadith 1509]
 [Sahih al-Muslim, 945]< Back to Questions