Sa'd ibn Mu'adh
Sa’d ibn Mu'adh (Arabic: سعد ابن معاذ) was the chief of the Banu Aus tribe in Medina and one of the prominent companions of Muhammad during early Medininian period who died shortly after the Battle of the Trench.
Acceptance of Islam
Sa'd adopted Islam in 622 (1 AH), when Muhammad arrived in Medina, then known as Yathrib. He was among the leading figures among the Ansar, as Muhammad had dubbed the people of Aws and Khazraj from Medina who converted to Islam.
Confrontation with Abu Jahl and start of Badr hostilities
Prior to the Battle of Badr, Sa’d had visited Mecca once to perform his Umra with his non-Muslim friend Umayah ibn Khalaf, when they came across Abu Jahl. They had an argument, and as it became heated, Sa'd threatened Abu Jahl with stopping the Meccan trade route to Syria if he stopped the Muslims from performing pilgrimage in Mecca. Narrated 'Abdullah bin Mas'ud:
Sa'd bin Mu‘ādh came to Mecca with the intention of performing 'Umra, and stayed at the house of Umaiya bin Khalaf Abi Safwan, for Umaiya himself used to stay at Sa'd's house when he passed by Medina on his way to Sham (i.e. Syria) .
Umaiya said to Sad, "Will you wait till midday when the people are (at their homes), then you may go and perform the Tawaf round the Ka'ba?"
So, while Sad was going around the Ka'ba, Abu Jahl came and asked, "Who is that who is performing Tawaf?"
Sad replied, "I am Sa'd." Abu Jahl said, "Are you circumambulating the Ka'ba safely although you have given refuge to Muhammad and his companions?" Sad said, "Yes," and they started quarreling.
Umaiya said to Sa'd, "Don't shout at Abi-l-Hakam (i.e. Abu Jahl), for he is chief of the valley (of Mecca)." Sad then said (to Abu Jahl). "By Allah, if you prevent me from performing the Tawaf of the Ka'ba, I will spoil your trade with Sham."
Umaiya kept on saying to Sa'd, "Don't raise your voice." and kept on taking hold of him. Sa'd became furious and said, (to Umaiya), "Be away from me, for I have heard Muhammad saying that he will kill you."
Umaiyya said, "Will he kill me?" Sad said, "Yes." Umaiya said, "By Allah! When Muhammad says a thing, he never tells a lie." Umaiya went to his wife and said to her, "Do you know what my brother from Yathrib (i.e. Medina) has said to me?" She said, "What has he said?" He said, "He claims that he has heard Muhammad claiming that he will kill me." She said, "By Allah! Muhammad never tells a lie."
So when the Meccans started to proceed for Badr (Battle) and declared war (against the Muslims), his wife said to him, "Don't you remember what your brother from Yathrib told you?" Umaiya decided not to go but Abu Jahl said to him, "You are from the nobles of the valley of Mecca), so you should accompany us for a day or two." He went with them and thus was killed.
Battle of Badr
The Muslims originally expected a much smaller Meccan force, but were suprised by the large Meccan Army so the Prophet called Shura:
When the Muslim army missed the caravan and the Quraysh army, between nine hundred and one thousand strong, helmeted and drawing closer, Abu Bakr stood up and said something good.
Several more Muhajirin also spoke, all the while the Messenger of Allah repeated: "advise me, O Muslims!", inquiring of what the Ansar, the majority then, had to say.
Then Sa`d bin Mu`adh said, "It looks like you mean us, O Messenger of Allah! By He Who has sent you with the Truth! If you seek to cross this sea and went in it, we will follow you and none among us will remain behind. We would not hate for you to lead us to meet our enemy tomorrow. We are patient in war, vicious in battle. May Allah allow you to witness from our efforts what comforts your eyes. Therefore, march forward with the blessing of Allah.
The Messenger of Allah was pleased with the words of Sa`d and was encouraged to march on. 
Battle of Uhud
Sa'd was one of the few companions who remained on the battlefield, when the Meccans led Khalid bin Walid counter attacked the unsuspecting Muslims and fought fiercely against the attacking Meccans. He later met up with Muhammad and was part of the small contingent Muslims defending him.
Battle of Trench and Qurayza
After the Battle of the Trench in 627 (5 AH), when Medina was unsuccessfully besieged by the Meccan army, the Banu Qurayza had treacherous dealings with the enemy.  Later the Muslims laid siege to their stronghold and the Banu Qurayza surrendered unconditionally after several weeks of siege.
Several members of the Banu Aus pleaded for their old Jewish allies and agreed to Muhammad's proposal that one of their chiefs should judge the matter. Banu Qurayza, themselves appointed Sa'd, and declared they will agree with whatever was Sa'd's verdict, the Verdict was consistent with the Bible [note 1] and some scholars claim the verdict was based on the Bible.
Some people (i.e. the Jews of Bani bin Quraiza) agreed to accept the verdict of Sad bin Muadh so the Prophet sent for him (i.e. Sad bin Muadh). He came riding a donkey, and when he approached the Mosque, the Prophet said, "Get up for the best amongst you." or said, "Get up for your chief." Then the Prophet said, "O Sad! These people have agreed to accept your verdict." Sad said, "I judge that their warriors should be killed and their children and women should be taken as captives." The Prophet said, "You have given a judgment similar to Allah's Judgment (or the King's judgment)."
Sa'd had been wounded in the earlier battles, and was on the verge of death. Sa'd succumbed to the wounds and died after returning to Medina.
He dutifully served as a member of the Muslim community and even commanded military campaigns for the Prophet during his lifetime. Saad is said to have been a stern, just and passionate man, willing to impulsively fight for what he believed in. In Muslim history, he is well regarded as a noble companion who enjoyed a close relationship with the Prophet.
I heard the Prophet saying, "The Throne (of Allah) shook at the death of Saad bin Muadh." Through another group of narrators, Jabir added, "I heard the Prophet : saying, 'The Throne of the Beneficent shook because of the death of Saad bin Muadh."
Even after his death Muhammad made constant references praising him:
A silken cloth was given as a present to the Prophet . His companions started touching it and admiring its softness. The Prophet said, "Are you admiring its softness? The handkerchiefs of Sad bin Muadh (in Paradise) are better and softer than it."
- Sahih al-Bukhari, 5:59:286
- Ibn Ishaq, (Collected by By Shaykh Safiur Rahman Al Mubarakpuri). Tafsir Ibn Kathir (Volume 3). Darussalam. p. 145. ISBN 9789960892740. Retrieved Jan 19, 2015.
- "Mubarakpuri, The Sealed Nectar, Chapter Al-Ahzab Invasion
- A Life of Mahomet and History of Islam to the Era of the Hegira, volume 3, page.
- Mohammed Abu-Nimer (2000–2001). "A Framework for Nonviolence and Peacebuilding in Islam". Journal of Law and Religion 15 (1–2): 247. doi:10.2307/1051519.
- Hashmi, Sohail H.; Buchanan, Allen E; Moore, Margaret (2003). States, Nations, and Borders: The Ethics of Making Boundaries. Cambridge University Press.
- Khadduri, Majid (1955). War And Peace in the Law of Islam. Baltimore: Johns Hopkins Press.
- Ahmad, Mirza Bashiruddin Mahmud. LIFE OF MUHAMMAD (PDF). p. 100-101. ISBN 978-1853720451. Retrieved Jan 20, 2015.
- Sahih al-Bukhari, 5:58:148
- Sahih al-Bukhari, 5:58:147
- Sahih al-Bukhari, 5:58:146
- When you march up to attack a city, make its people an offer of peace. If they accept and open their gates, all the people in it shall be subject to forced labor and shall work for you. If they refuse to make peace and they engage you in battle, lay siege to that city. When the Lord your God delivers it into your hand, put to the sword all the men in it. As for the women, the children, the livestock and everything else in the city, you may take these as plunder for yourselves. And you may use the plunder the Lord your God gives you from your enemies. This is how you are to treat all the cities that are at a distance from you and do not belong to the nations nearby. However, in the cities of the nations the Lord your God is giving you as an inheritance, do not leave alive anything that breathes. Completely destroy them—the Hittites, Amorites, Canaanites, Perizzites, Hivites and Jebusites—as the Lord your God has commanded you. Otherwise, they will teach you to follow all the detestable things they do in worshiping their gods, and you will sin against the Lord your God.(Deut. 20: 10-18)