The difference between a nabi (prophet) and a rasul (messenger)
Question

Is there a difference between a nabi (prophet) and a rasul (messenger)?
Praise be to Allah.The scholars differed regarding that. Some of them said that there is no difference between a nabi and a rasul, and others said that there is a difference between a nabi and a rasul.
The latter is the correct view, because the basic principle in speech is to establish ideas, not to repeat ideas for the purpose of emphasis.
Abu’l-Baqa’ al-Kafawi said in al-Kulliyyat (p.1065): Establishing ideas is more important than repeating ideas for the purpose of emphasis, because establishing new ideas is better than mere repetation. End quote.
Then the scholars differed with regard to how these differences are to be defined and explained.
The most well-known view is that a nabi and a rasul both receive revelation, but the rasul is commanded by Allah to convey it, whereas the nabi is not commanded to convey it.
Al-Khattabi said in A‘lam al-Hadith (1/298): The difference between the nabi and the rasul is that the nabi is the one who is told or informed about things, whereas the rasul is the one who is enjoined to convey what he is told and informed about. Hence every rasul is a nabi but not every nabi is a rasul. End quote.
Ibn Hajar said in Fath al-Bari (11/112): al-Qurtubi said, following the view of others: This is proof for those who do not allow the transmission of hadiths on the basis of meaning, and it is the correct view among the Malikis, because the words nabi and rasul come from different roots.
The word nabi comes from the root naba’, which refers to news. Thus the nabi is the one who is told by Allah a command that becomes like an obligation. If he is commanded to convey [what he is told] to others, then he is a rasul, otherwise he is a nabi and not a rasul. Based on that, every rasul is a nabi, but the opposite is not the case. Thus the nabi and the rasul have something in common, which is receiving news, but they differ with regard to conveying the message. So if you say that So and so is a rasul, this implies that he is a nabi and rasul; but if you say that So and so is a nabi, this does not imply that he is a rasul. End quote.
Ibn al-Mulaqqin said in al-Mu‘in ‘ala Tafahhum al-Arba‘in (p. 39): Rusul is the plural of rasul, which refers to the one who is commanded to convey the revelation to people; this is more specific than the word nabi. Thus he [the rasul] is the one who receives revelation to act upon and convey, in contrast to the nabi, who receives revelation to act upon it only. End quote.
Some of the scholars say that both receive revelation and both are commanded to convey it, but the rasul has a book from Allah. Other scholars say that the rasul is the one to whom a book comes down, or to whom an angel comes, whereas the nabi is the one who receives revelation, or follows another rasul.
Al-‘Ayni said in al-Binayah Sharh al-Hidayah (1/116): The difference between the rasul and the nabi is that the rasul is the one who is sent to convey the revelation and has a book, whereas the nabi is the one who is sent to convey revelation in general terms, either with or without a book. This was stated by Shaykh Qawwam ad-Din al-Atrazi in his Sharh…
Then he said: The correct view in this case is that the rasul is the one to whom a book comes down, or an angel comes to him, whereas the nabi is the one whom Allah, may He be exalted, informs of the rulings, or he follows another rasul. End quote.
Perhaps the best that may be said concerning this matter is:
The nabi and rasul have in common the fact that they both receive revelation. This is indicated by the verse in which Allah, may He be exalted, says (interpretation of the meaning):
{Indeed, We have revealed to you, [O Muhammad], as We revealed to Noah and the prophets after him. And we revealed to Abraham, Ishmael, Isaac, Jacob, the Descendants, Jesus, Job, Jonah, Aaron, and Solomon, and to David We gave the book [of Psalms]} [an-Nisa’ 4:163].
They also have in common the fact that they are both commanded to convey the message, as mentioned in the verse in which Allah, may He be exalted, says (interpretation of the meaning):
{And We did not send before you any messenger or prophet except that when he spoke [or recited], Satan threw into it [some misunderstanding]. But Allah abolishes that which Satan throws in; then Allah makes precise His verses. And Allah is Knowing and Wise} [Al-Hajj 22:52].
Shaykh ash-Shinqiti said in Adwa’ al-Bayan (5/290): This verse of Soorat al-Hajj indicates that what is commonly known among the people of knowledge, that the nabi is the one who receives revelation and is not enjoined to convey it, whereas the rasul is the nabi who receives revelation and is commanded to convey what is revealed to him, is not correct, because the words {And We did not send before you any messenger or prophet …} indicate that both are sent, but there is some difference between them.
Some of the scholars suggested that the nabi who is also a rasul is the one to whom a book and an independent system of law are sent down, in addition to miracles which prove that he is a true prophet, whereas the nabi who is sent, who is different from a rasul, is the one to whom no book is sent down; rather he receives revelation telling him to call people to the system of law of the rasul who came before him. An example of that is the Israelite prophets who were sent and instructed to act in accordance with the Torah, as Allah, may He be exalted, states in the verse (interpretation of the meaning): {The prophets who submitted [to Allah ] judged by it …} [al-Ma’idah 5:44]. End quote.
The rasul and nabi differ in that the rasul is enjoined to convey the message to one of the disbelieving nations. As for the nabi, he is enjoined to convey the message and call people, without having a separate message for a new nation among those who reject the truth.
Shaykh al-Islam said in an-Nubuwwat (2/714): The nabi is the one to whom Allah sends revelation, which carries a message from Allah. If, in addition to that, he is sent to those who go against the command of Allah, to convey a message from Allah to them, then he is a rasul.
But if he is sent to implement the system of law that came before him, and he is not sent to anyone to convey a message from Allah to him, then he is a nabi, and not a rasul. Allah, may He be exalted, says (interpretation of the meaning): {And We did not send before you any messenger or prophet except that when he spoke [or recited], Satan threw into it [some misunderstanding]} [Al-Hajj 22:52].
The words {any messenger or prophet} mention the idea of sending in general terms, which includes both types. One of them is called a rasul, which refers to a messenger in a general sense whom Allah instructs to convey His message to those who opposed Him, such as Nuh. It is affirmed in the sahih hadiths that he was the first messenger (rasul) sent to the people of Earth, and that before him there were prophets (anbiya’), such as Shith and Idris (peace be upon them), and before them there was Adam, to whom Allah spoke directly. Ibn ‘Abbas said: Between Adam and Nuh there were ten generations, each of whom followed Islam.
Those prophets (anbiya’) received revelation from Allah telling them what they should do, and they instructed the believers who followed them to do the same, because they believed in them, just as the followers of a system of law accept what the scholars convey from the rasul.
Another example of that is the Israelite prophets, who enjoined the system of law of the Torah, one of whom might receive revelation specifically for him to keep to himself and not convey, regarding a specific incident. But with regard to the Torah system of law, they were like scholars whom Allah enabled to work out an issue in the light of the Torah, just as Allah enables Muslim scholars to understand some matter in accordance with the Quran, and Allah enabled Sulayman to work out a ruling on the matter that he judged along with Dawud.
Thus Allah informed the prophets (anbiya’) of His commands and prohibitions, and other matters, and they told those who believed in them what Allah told them of news, commands and prohibitions.
But if they were sent to the disbelievers to call them to affirm Allah’s oneness and worship Him alone, with no partner or associate, there would inevitably be some people who would reject and deny the messengers (rusul). Allah, may He be exalted, says (interpretation of the meaning):
{Similarly, there came not to those before them any messenger except that they said, “A magician or a madman”}[adh-Dhariyat 51:52]
{Nothing is said to you, [O Muhammad], except what was already said to the messengers before you}[Fussilat 41:43].
The messengers (rusul) were sent to people who opposed the divine message, and some of them rejected that message. Allah says:
{And We sent not before you [as messengers] except men to whom We revealed from among the people of cities. So have they not traveled through the earth and observed how was the end of those before them? And the home of the Hereafter is best for those who fear Allah; then will you not reason?
 [They continued] until, when the messengers despaired and were certain that they had been denied, there came to them Our victory, and whoever We willed was saved. And Our punishment cannot be repelled from the people who are criminals}[Yusuf 12:109-110]
{Indeed, We will support Our messengers and those who believe during the life of this world and on the Day when the witnesses will stand} [Ghafir 40:51].
The verse {And We did not send before you any messenger or prophet …} [al-Hajj 22:52] indicates that the nabi is sent, but is not usually called a rasul, because he was not sent to people with something that they did not know. Rather he would enjoin the believers to adhere to what they knew to be true, as a scholar does.
Hence the Prophet (blessings and peace of Allah be upon him) said: “The scholars are the heirs of the prophets.” It is not stipulated that a rasul should bring a new system of law; Yusuf followed the path of Ibrahim, and Dawud and Sulayman were messengers (rasul), although they followed the system of law of the Torah. And Allah, may He be exalted, tells us that the believer of the household of Pharaoh said (interpretation of the meaning):
{“And Joseph had already come to you before with clear proofs, but you remained in doubt of that which he brought to you, until when he died, you said, ‘Never will Allah send a messenger after him.’} [Ghafir 40:34].
End quote.
And Allah knows best.