Mu'adh ibn Jabal
From the Alim Software

Narrated Mu'adh ibn Jabal:

When Allah's Messenger (peace be upon him) sent him to the Yemen,
he went out with him giving him advice, Mu'adh riding 
and Allah's Messenger (peace be upon him) walking beside his riding beast. 
Then when he finished he said, 
"Perhaps, Mu'adh, you may not meet me after this year, 
but perhaps, you may pass this mosque of mine and my grave.
Mu'adh wept from grief over the departure of 
Allah's Messenger (peace be upon him). The Prophet (peace be upon him) 
then turned facing Medina and said, 
"Those nearest to me are the pious, whoever they are and whenever they are."

Narrated AbuHurairah:

Allah's Apostle (peace be upon him) said: 
Don't nurse [a] grudge and don't bid him out 
for raising the price and 
don't nurse aversion or enmity 
and don't enter into a transaction when
others have entered into that transaction 
and be as fellow-brothers and servants of Allah. 
A Muslim is the brother of a Muslim. 
He neither oppresses him nor humiliates him nor looks down upon him. 
The piety is here,
(and while saying so) he pointed towards his chest thrice.
It is a serious evil for a Muslim 
that he should look down upon his brother Muslim. 
All things of a Muslim are inviolable for his brother in faith; 
his blood, his wealth and his honour.

About Mu'ad ibn Jabal, r.a.

Mu'adh ibn Jabal was a young man growing up in Yathrib [Medina today] as the light of guidance and truth began to spread over the Arabian peninsula. He was a handsome and imposing character with black eyes and curly hair and immediately impressed whomever he met. He was already distinguished for the sharpness of his intelligence among young men of his own age.

The young Mu'adh became a Muslim at the hands of Musab bin Umayr, the daiy (missionary) whom  the Prophet had sent to Yathrib before the hijrah [migration]. Mu'adh was among the 72 Yathribites who journeyed to Makkah [Mecca] one year before the hijrah, and met the Prophet at his house and later again in the valley of Mina, outside Makkah, at Aqabah. Here the famous second Aqabah Pledge was made at which the new Muslims of Yathrib, including some women, vowed to support and defend the Prophet at any cost. Mu'adh was among those who enthusiastically clasped the hands of the blessed Prophet then and pledged allegiance to him.

As soon as Mu'adh returned to Yathrib from Makkah, he and a few others of his age formed a group to remove and destroy [the] idols from the houses of the mushrikin [polytheists] in Yathrib. One of the effects of this campaign was that a prominent man of the city, Amr bin al-Jumuh, became a Muslim.

When the noble Prophet reached Yathrib, Mu'adh bin Jabal stayed in his company as much as possible. He studied the Qur'an and the laws of Islam until he became one of the most well-versed of all the companions in the religion of Islam.

Wherever Mu'adh went, people would refer to him for legal judgments on matters over which they differed. This is not strange since he was brought up in the school of the Prophet himself and learnt as much as he could from him. He was the best pupil of the best teacher. His knowledge bore the stamp of authenticity. The best certificate that he could have received came from the Prophet himself when he said, "The most knowledgeable of my ummah [community] in matters of Halal [permitted, allowed, lawful or legal] and Haram [forbidden] is Mu'adh bin Jabal."

One of the greatest of Mu'adh's contributions to the ummah of Muhammad was that he was one of the group of six who collected the Qur'an during the lifetime of the Prophet, peace be upon him. Whenever a group of companions met and Mu'adh was among them, they would look at him with awe and respect on account of his knowledge. The Prophet and his two Khalifahs after him placed this unique gift and power in the service of Islam .

After the liberation of Makkah, the Quraysh became Muslims en masse. The Prophet immediately saw the need of the new Muslims for teachers to instruct them in the fundamentals of Islam and to make them truly understand the spirit and letter of its laws. He appointed Attab bin Usay as his deputy in Makkah and he asked Mu'adh bin Jabal to stay with him and teach people the Qur'an and instruct them in the religion.

Sometime after the Prophet had returned to Yathrib, messengers of the kings of Yemen came to him announcing that they and the people of Yemen had become Muslims. They requested that some teachers should be with them to teach Islam to the people. For this task the Prophet commissioned a group of competent duat (missionaries) and made Mu'adh bin Jabal their amir. He then put the following question to Mu'adh:

"According to what will you judge?"
"According to the Book of God," replied Mu'adh.
"And if you find nothing therein?"
"According to the Sunnah of the Prophet of Gtd."
"And if you find nothing therein?"
"Then I will exert myself (exercise ijtihad) to form my own judgment."

The Prophet was pleased with this reply and said: "Praise be to God Who has guided the messenger of the Prophet to that which pleases the Prophet."

The Prophet personally bade farewell to this mission of guidance and light and walked for some distance alongside Mu'adh as he rode out of the city. Finally he said to him: O Mu'adh, perhaps you shall not meet me again after this year. Perhaps when you return you shall see only my mosque and my grave." Mu'adh wept. Those with him wept too. A feeling of sadness and desolation overtook him as he parted from his beloved Prophet, peace and blessings of God be on him.
The Prophet's premonition was correct. The eyes of Mu'adh never beheld the Prophet after that moment. The Prophet died before Mu'adh returned from the Yemen. There is no doubt that Mu'adh wept when he returned to Yathrib and found there was no longer the blessed company of the Prophet.

During the caliphate of Umar, Mu'adh was sent to the Banu Kitab to apportion their stipends and to distribute the sadaqah [alms-giving] of their richer folk among the poor. When he had done his duty, he returned to his wife with his saddle blanket around his neck, empty handed, and she asked him:

"Where are the gifts which [the] commissioners return with for their families?" "I had an alert Supervisor who was checking over me," he replied. "You were a trusted person with the messenger of God and with Abu Bakr. Then Umar came and he sent a supervisor with you to check on you!' she exclaimed. She went on to talk about this to the women of Umar's household and complained to them about it. The complaint eventually reached Umar, so he summoned Mu'adh and said:

"Did I send a supervisor with you to check on you?"

"No, Amir al-Muminin," [commander of the Faithful] he said, "But that was the only reason I could find to give her." Umar laughed and then gave him a gift, saying, "I hope this pleases you."

Also during the caliphate of Umar, the governor of Syria, Yazid bin Abu Sufyan sent a message saying: "O Amir al-Mumineen! The people of Syria are many. They fill the towns. They need people to teach them the Qur'an and instruct them in the religion."

Umar thereupon summoned five persons who had collected the Qur'an in the lifetime of the Prophet, peace be upon him. They were Mu'adh bin Jabal, Ubadah bin as-Samit, Abu Ayyub al-Ansari, Ubayy bin Kab and Abu al-Darda. He said to them:
"Your brothers in Syria have asked me to help them by sending those who can teach them the Qur'an and instruct them in the religion. Please appoint three among you for this task and may God bless you. I can select three of you myself if you do not want to put the matter to the vote."

"Why should we vote?" they asked. "Abu Ayyub is quite old and Ubayy is a sick man. That leaves three of us." "All three of you go to Homs first of all. If you are satisfied with the condition of the people there, one of you should stay there, another should go to Damascus and the other to Palestine."

So it was that Ubadah bin as-Samit was left at Homs, Abu al-Darda went to Damascus and Mu'adh went to Palestine. There Mu'adh fell ill with an infectious disease. As he was near to death, he turned in the direction of the Kabah and repeated this refrain: "Welcome Death, Welcome. A visitor has come after a long absence . . ." And looking up to heaven, he said: "O Lord, You know that I did not desire the world and to prolong my stay in it . . . O Lord, accept my soul with goodness as You would accept a believing soul..."

He then passed away, far from his family and his clan, a daiy in the service of God and a muhajir in His path.

His tomb is at Ghor in the Jordan Valley.  He died there 18 years after the Hijra at the age of 38. 

For a communication from the Prophet pbuh to Mu'adh ibn Jabal r.a, upon the death of Mu'adh's son click here

For narrations about and by Mu'adh ibn Jabal [in some Hadith] click here