Muadh was a young man living in Medina when the city was still known as Yathrib. He was introduced to Islam by Musab ibn Umayr, the man Prophet Muhammad, may the peace and blessings of God be upon him, sent to Yathrib well before the mass migration of the Muslims from Mecca to Yathrib. Musab was essentially Prophet Muhammad’s ambassador, and his mission was to teach a small group of believers who had pledged allegiance to Islam. However, the light of Islam was spreading rapidly in Yathrib, and among those newcomers to the fledgling nation was Muadh ibn Jabal, a young man with dark eyes and black curly hair.
When Muadh was around 17 years of age, he was among the seventy-two people from Yathrib who journeyed to Mecca to meet Prophet Muhammad. At this time, the second Aqabah pledge was made, and Muadh was one of the believers who clasped the hands of Prophet Muhammad pledging allegiance to him, vowing to support and defend him at any cost. When Muadh returned to Yathrib, he, with others around his own age, formed a group to remove and destroy many idols around the city. As a consequence of this, a prominent man in Yathrib, Amr ibn al-Jumuh, embraced Islam.
About one year later, Prophet Muhammad took up residence in Yathrib, and Muadh tried to stay in his company as much as possible. He listened carefully and tried to emulate the Prophet. This behavior enabled Muadh to become very knowledgeable in all aspects of Islam. His knowledge and eloquence became well known and respected, even though he was relatively young.
Prophet Muhammad recognized his knowledge and mentioned him often. He said, "Learn the recitation of the Quran from four people, Ibn Masood, Salim, the freed slave of Hudhaifah, Ubayy, and Muadh ibn Jabal."
In another saying, Muadh is mentioned among some of the most learned men in the history of Islam. "The most merciful person from my nation, to my nation is Abu Bakr; the sternest of them regarding God’s commands is Umar; the shyest is Uthman; the most knowledgeable regarding the recitation of the Quran is Ubayy ibn Kab; the most dutiful is Zaid ibn Thabit and the most knowledgeable of them as regards the permissible and the impermissible is Muadh ibn Jabal..."
Among his many achievements, Muadh was one of six men who collected the Quran while Prophet Muhammad was still alive. Due to his vast knowledge, he was appointed to teach the Meccans that converted to Islam en masse after the liberation of Mecca.
After Prophet Muhammad had returned to Yathrib, now known as Medina, messengers came to him from Yemen. They informed him that many people in Yemen had become Muslim and requested that he send someone to teach and instruct them. Prophet Muhammad organized a group of missionaries and made Muadh their leader. A fitting task for the man who Prophet Muhammad called, the man who will lead the scholars into Paradise.
Prophet Muhammad’s advice to Muadh is still used today as a guide on introducing Islam to others. Muadh was instructed to teach Islam in gradual steps, starting with the most important beliefs, the testimony of faith and monotheism, and moving on to the pillars of prayer and charity.
"Verily, you are coming to People of the Book, so call them to testify there is no deity but Allah and I am the Messenger of Allah. If they accept that, then teach them that God has obligated five prayers in each day and night. If they accept that, then teach them that God as obligated charity to be taken from the rich and given to the poor. If they accept that, beware not to take from the best of their wealth. Be on guard from the supplication of the oppressed, for there is no barrier between it and God."
During the preparations for Muadh’s trip, he and Prophet Muhammad discussed how he (Muadh) would decide judgments and handle any disputes. Muadh’s answer was concise and is considered best practice in any Islamic society. He replied, "‘I will refer to the Quran.’ The Prophet then asked, ‘What will you do if you do not find the decree you are looking for in the Quran?’ Muadh answered, ‘I will refer to your Sunnah.’ The Prophet then asked, ‘But what will you do if you do not find a decree even in my Sunnah?’ Muadh answered, ‘I will judge between people using reasoning.’"
Both these sayings about Muadh’s journey to Yemen are very well known. The first explains how to call people to Islam, and the second explains how to judge between people and make rulings. Prophet Muhammad sent Muadh on his mission warning him that it might be the last time he saw him (Prophet Muhammad) alive. Muadh wept and with a mixture of sadness and hope he left his beloved Prophet and went to live in Yemen, staying there for some years.
Muadh was known to be a generous man. He would regularly give all his money to anyone who needed help. In Yemen, he helped to shape a well-ordered Muslim community. One year, when Umar ibn al-Khattab was the leader of the Muslim nation, Muadh sent one-third of the charitable donations of Yemen to Medina. This action upset Umar, and he admonished Muadh, saying that he was sent to take from the rich and give to the poor, not to be a tax-collector. To this, Muadh replied, "I would not send you anything had I found someone to take it from me." The next year, Muadh sent half of the charity from Yemen for the same reason. And the year after that, he sent all of the charity from Yemen to Medina, saying that he did not find a single person in Yemen who was eligible for the collected charity.
Later in Umar’s caliphate, Muadh was sent to Syria to advise and teach. When Abu Ubaidah, the governor of Syria and a close friend of Muadh’s, died, Umar ibn al-Khattab assigned Muadh to take his place as governor. Within a few months of his appointment, Muadh fell ill. It is said that when he understood that he was dying, he turned to face Mecca and said, "Welcome death, you are long-awaited and beloved."
Source: Islam Religion