Abdullah bin Mas’ud (r.a.)
Abdullah was a young shepherd. He used to herd the sheep of Aqaba bin Abi Muit. One day, while he was with the sheep, two guests arrived. The guests told him they were thirsty and asked him for milk. The young shepherd said to them,
"Yes, there is milk but I cannot give you! These sheep have been entrusted to me. I cannot give you milk before I ask permission from the owner. Otherwise, I will have misappropriated."
Thereupon, the guests wanted from the shepherd, who was a child, a female goat that had never copulated with a male goat. The shepherd brought a goat like that to them. One of the guests held the goat and prayed. The other started to milk the goat. It looked as the udders became full of milk suddenly. They took a bowl and filled it with milk. They drank the milk and quenched their thirst; the person who milked the goat prayed again; the goat returned to its previous state.
The young shepherd, who did not know that one of them was the Messenger of Allah (pbuh) and the other was Abu Bakr, asked in excitement,
"Will you teach me what you read?"
The Messenger of Allah put his blessed hand on the shepherd and said,
"You are a taught young man."
And this child, who received prayer of the Messenger of Allah as soon as he entered Islam, became superior to all of the Companions in terms of reading the Qur'an and became famous as one of the "Six Abdullahs".
Yes, this innocent and sensitive shepherd was Abdullah bin Mas'ud. Thus, he received the honor of being one of the first Muslims.
When the pressure of the polytheists increased in Makkah, the Companions came together and started complaining that they could not read the Quran aloud in the presence of Qurayshis. Hz. Abdullah said,
"I will read the Quran aloud to them." The others said,
"We fear that they will do something bad to you." They said that they found it better if someone from a strong tribe read it. Abdullah said,
"Allow me to read. Allah will protect me." He went out and went to the place where the polytheists of Quraysh gathered near the Kaaba. He said Bismillah and started to read the beginning of the chapter of ar-Rahman.
The polytheists were astonished first; then, their astonishment was transformed into fury; they approached Abdullah and began to hit him on the face. However, Abdullah did not stop; he continued reading. Then, he returned to his friends. When his friends ran toward him anxiously, Abdullah said:
"By Allah! There are no people simpler than these among the enemies of Allah in my sight. If you want, I will go and do the same thing tomorrow. "
Abdullah, who was a young and weak shepherd but turned out to assume a spiritual power that could challenge the world after finding the secret of belief, clearly showed that he disregarded the so-called great leaders of Makkah and humiliated them all. Thus, the goal was attained. Therefore, the Companions did not consider it appropriate for Hz. Abdullah to go there again the next day and risk his life. 
Abdullah bin Mas'ud was one of the Companions who gained the virtue of migrating twice. When the tortures of the polytheists became unbearable, he migrated to Abyssinia. However, he missed the Prophet a lot and returned to Makkah after a while. When the permission to migrate was given, he migrated to Madinah. The Messenger of Allah (pbuh) made him brothers with Zubayr bin Awwam.
The Prophet made Abdullah stay in a place next to the mosque. For this reason, he always served the Messenger of Allah. He always walked with the Prophet, helped him put on his shoes and carried his things like his staff, pillow, perfume and miswak. When the Prophet slept, Abdullah Ibn Mas’ud would wake him up. Therefore, the Companions called him "Sahibus-Sawad was-Siwak". Hz. Abdullah was together with the Messenger of Allah so frequently that the people who came to Madinah first thought he was from Ahl al-Bayt. The famous Companion, Abu Musa al-Ashari, who came to Madinah after the Conquest of Khaybar states the following regarding the issue:
"When my brother and I came to Madinah first, we thought that Abdullah and his mother were from Ahl al-Bayt because he entered the house of the Messenger of Allah so frequently." 
He was asked who was the closest person to him as a guide. He said, “The person closest to the Messenger of Allah in terms of being a guide and in terms of character is Abdullah Ibn Mas'ud.”
We learn another narration about his closeness to the Messenger of Allah from Abdurrahman bin Yazid. He states the following regarding the issue:
“Once, we asked Hudhayfa al-Yaman, ‘Who is the closest Companion to the Messenger of Allah in terms of living style? We want to accept him as a model.’ Hudhayfa said, ‘The Companion who is closest to the Messenger of Allah in terms of lifestyle and character is Abdullah Ibn Mas’ud. We do not know anybody else.’”
Hz. Abdullah read the Quran in a very nice way. The Prophet advised the Companions to learn the Quran from four people. One of them was Hz. Abdullah. 
According to a narration in Bukhari, the Prophet Muhammad asked Hz. Abdullah to read him the Quran. Thereupon, Ibn Mas'ud said,
"O Messenger of Allah! Shall I read you the Quran though it was sent down to you?" The Prophet said,
"Yes, I like to hear it from someone else!"
Ibn Mas'ud began to read. When he read up to the verse “How then if We brought from each people a witness, and We brought thee as a witness against these people?, the Messenger of Allah said,
"That is enough for now." Tears were coming from his eyes. 
Abdullah bin Mas’ud had a different place in the eye of the Prophet. Once, he said,
“Follow two people after me: Abu Bakr and Umar. Follow the way that Ammar shows. Follow the advice of Ibn Mas’ud fully.”
Once, Hz. Abdullah climbed a tree to get something. Meanwhile, his legs, which were very thin, were seen. Some of the Companions laughed when they saw this. Our Prophet did not like their act and said,
"Why are you laughing? Abdullah's legs will be heavier than Mount Uhud on the Day of Judgment." 
Ibn Mas'ud participated in all wars with our Prophet. He fought heroically. He cut off the head of Abu Jahl, whom he found in a wounded state in the Battle of Badr and took it to the Messenger of Allah. He participated in the Battle of Yarmuk after the death of the Prophet.
Hz. Abdullah, who was one of the students of Suffa, who was in close terms with the Messenger of Allah, who did not leave the Prophet alone except for obligatory situations, who devoted his life to the Quran and who could enter into the presence of the Messenger of Allah without taking permission, had a unique understanding of ilm. He states the following regarding the issue:
"I swear by Allah that there is no chapter from the Book of Allah that I am not the one who knows the best where it was sent down! There is no verse that I am not the one who knows the best why it was sent down. If I knew that there was someone who knew the Book of Allah better than me in a place where I can go on a camel, I would mount my camel and go there. "
Ibn Mas'ud (r.a.) was also famous in the ilm of hadith. He narrated 848 hadiths. When he narrated hadiths, he acted very cautiously. His face would fade and change color. He did not usually speak definitely by saying "the Messenger of Allah said." He feared that he would attribute lies to the Prophet. Some of the hadiths he reported are as follows:
“The Messenger of Allah (pbuh) said, ‘He who has in his heart the weight of a mustard seed of pride shall not enter Paradise.’ Thereupon, somebody said, ‘Verily a person loves that his dress should be fine, and his shoes should be fine.’ The Messenger of Allah remarked, ‘Verily, Allah is Graceful and He loves Grace. Pride means disdaining the truth out of self-conceit and contempt for the people.’”. 
“Adhere to truthfulness. Truthfulness definitely leads to righteousness, and righteousness leads to Paradise. And a man keeps on telling the truth until he becomes a truthful person. Avoid telling lies because a man may keep on telling lies till he is recorded as a liar before Allah.” 
“Whoever suffers from destitution and he beseeches the people for it, his destitution shall not end. And whoever suffers from destitution and he beseeches Allah for it, Allah will send provisions to him, sooner or later.” 
“No Muslim is afflicted with harm because of sickness or some other inconvenience, but that Allah will remove his sins for him as a tree sheds its leaves.” 
Hz. Abdullah had an exceptional place in the science of fiqh. He issued many fatwas. A great scholar like Abu Musa al-Ash'ari respects his knowledge regarding the issue. He said, "Do not ask me anything when Ibn Mas'ud is with you." Hz. Umar complimented on him by saying, “Ibn Mas’ud is a leather bag filled with ilm."
Abdullah was both a good scholar and a good teacher. He taught what he knew to others in the best way. In an assembly where Hz. Ali was present, somebody said, "We have never seen a person having higher ethics than Abdullah, a person more compassionate about teaching, more pleasant in conversation, and more pious than Abdullah." Hz. Ali replied, "Yes. O Lord" Bear witness that I approve what they say and even more." 
Knowing his merits, Hz. Umar appointed him as a teacher in Kufa. He also wrote the following letter to the people of Kufa:
"I am sending you Ammar bin Yasir as an emir and Abdullah bin Mas'ud as a teacher. Both of them are among the distinguished ones of the Companions. Be subject to them, obey them and listen to their words. Know it that I preferred you regarding Abdullah Ibn Mas'ud."
With this last sentence, Hz. Umar said that he needed Abdullah often but he preferred the people of Kufa to his own self, stating that he gave him the opportunity to benefit from Ibn Mas’ud.
Fulfilling this duty in the best way, Ibn Mas'ud continued serving as a qadi and issuing fatwas during the caliphate of Hz. Uthman, too. In addition, he was an official of the Treasure. In those years, the needs of the mujahids who fought against the Byzantines were met by Kufa. Ibni Mas'ud fulfilled this duty very well too. When the movements of mischief became widespread during the last years of the caliphate of Hz. Uthman, he returned to Hejaz.
Hz. Abdullah was sick. Hz. Uthman visited him and asked if he had any complaints.
Abdullah Ibn Mas’ud said, "I have only one complaint; it is my sins!" Hz. Uthman asked Hz. Abdullah what he wanted. He said that he wanted Allah's mercy. Hz. Uthman said,
"Shall we get you something?" He gave a short answer:
"I do not need anything." Thereupon, Hz. Uthman said,
"You can leave it to your children." Abdullah said,
"Do you fear that my children will go hungry? I ordered them to read the chapter of al-Waqia every night. For, I heard the Messenger of Allah say, "Whoever reads the chapter of al-Waqia every night will not suffer from poverty in the world." 
Hz. Abdullah died at the age of 64 in 32 H. He was buried in the cemetery of Baqi.
Two of his noteworthy statements are as follows:
"It is better to prefer being poor to being rich through haram things. It is better to prefer being modest by obeying Allah to obtaining honor by disobeying Allah."
Abdullah said, "Never be an imma’a." They asked, "What is imma’a?" He gave the following response:
“An imma’a is a person who says, ‘I do not have a personal opinion. I do what people do. If they become Muslims, I will become a Muslim; if they become unbelievers, I will become an unbeliever, too.’ Say, 'Even if everybody becomes unbelievers, I am determined to remain a Muslim.'”
Usdul-Ghaba, 3: 257.
Muslim, Fadailus-Sahaba: 110; Tirmidhi, Manaqib: 38.
Tirmidhi, Manaqib: 38.
Bukhari, Fadailul-Qur’an: 32-33.
Tirmidhi, Manaqib: 38.
Tabaqat, 3: 155.
Muslim, Fadailus-Sahaba: 115.
Muslim, Iman: 147; Tirmidhi, Birr: 60.
Bukhari, Adab: 69; Muslim, Birr: 105.
Tirmidhi, Zuhd: 18.
Bukhari, Marda: 3; Muslim, Birr: 45.