For example, when 'Uthman ibn Mad'un died, the Messenger shed as many tears as he had over Hamza's corpse. He kissed his forehead and attended the funeral. Witnessing this, a woman said: "How happy you are, 'Uthman. You have become a bird to fly in Paradise." The Messenger turned to her and asked: "How do you know that, while I, a Prophet, do not know? Unless God informs, no one can know whether someone is pure enough to deserve Paradise and whether he will go to Paradise or Hell." The woman collected herself, and said that she would never make such an assumption again.  Is it conceivable that she and the Companions present at the funeral should have forgotten that event? They did not forget it, as well as others that they witnessed during the Prophet's lifetime.
Another example: Quzman fought heroically at Uhud, and was finally killed. The Companions considered him a martyr. However, the Prophet told them that Quzman had gone to Hell. Someone later informed them that Quzman had committed suicide because of his wounds, and had said before he died: "I fought out of tribal solidarity, not for Islam." The Messenger concluded: "God strengthens this religion even through a sinful man."  Like others, that event and his final comment could never have been forgotten by the Companions, nor could they have failed to mention it whenever they talked about Uhud or martyrdom.
A similar incident took place during the conquest of Khaybar. 'Umar reports: "On the day Khaybar was conquered, some Companions listed the martyrs. When they mentioned so-and-so as a martyr, the Messenger said: 'I saw him in Hell, for he stole a robe from the spoils of war before it was distributed.'" He then told me to stand up and announce: 'Only believers (who are true representatives or embodiments of absolute faith and trustworthiness) can enter Paradise.'" 
Each word and action of the Messenger refined the Companions' understanding and implementation of Islam. This motivated them to absorb his every word and action. When they settled in newly conquered lands, they conveyed their knowledge to the new Muslims, thereby ensuring that the Sunna would be transmitted from one generation to the next.
They were so well-behaved toward the Messenger that they would remain silent in his presence and let bedouins or others ask him questions. One day a bedouin named Dimam ibn Tha'laba came and asked rudely: "Which one of you is Muhammad?" They replied that he was the white-complexioned man sitting against the wall. The bedouin turned to him and asked loudly: "O son of 'Abd al-Muttalib, I will ask you some questions! They may be injurious to you, so don't become annoyed with me." The Prophet told him to ask whatever was in his mind. He said: "Tell me, for the sake of God, your Master and the Master of those before you, did He send you to these people as a Prophet?" When the Prophet said that this was true, Dimam asked: "Tell me, for God's sake, is it God Who ordered you to pray five times a day?" When the Prophet said that this was true, Dimam continued questioning him in the same manner about fasting and alms-giving. Always receiving the same answer, Dimam announced: "I am Dimam ibn Tha'laba, from the tribe of Sa'd bin Bakr. They sent me to you as an envoy. I declare that I believe in whatever message you have brought from God." 
Like many others, this event too was not allowed to fall into oblivion; rather, it was handed down to succeeding generations until it was recorded in the books of Tradition.
Ubayy ibn Ka'b was one of the foremost reciters of the Qur'an. One day the Messenger sent for him and said: "God ordered me to recite Surah al-Bayyina to you." Ubayy was so moved that he asked: "Did God mention my name?" The Messenger's answer moved him to tears.  This was so great an honor for Ubayy's family that his grandson would introduce himself as "the grandson of the man to whom God ordered His Messenger to recite Sura al-Bayyina."
This was the ethos in which the Companions lived. Every day a new "fruit of Paradise" and "gift" of God was presented to them, and every day brought new situations. Previously unaware of faith, Divine Scripture, and Prophethood, these desert Arabs, gifted with a keen memory and a talent for poetry, were brought up by the Messenger to educate future Muslim generations. God chose them as His Messenger's Companions, and willed them to convey His Message throughout the world. After the Prophet's death, they conquered in the name of Islam all the lands from Spain to China, from Caucasia to India, with unprecedented speed. Conveying the Qur'an and the Sunna everywhere they went, many of the conquered people joined their households and embraced Islam. The Muslims instructed these new Muslims in the Qur'an and the Sunna, thereby preparing the ground for all the leading Muslim scholars and scientists to come.
The Companions considered memorizing and transmitting the Qur'an and the Sunna as acts of worship, for they had heard from the Messenger say: "Whoever comes to my mosque should come either to learn the good or to teach it. Such people have the same rank as those who fight in the way of God." 
So, as Anas reports, they frequently met to discuss what they heard from the Messenger.  Women also were taught by the Messenger, who set aside a specific day for them. His wives actively conveyed to other women whatever they learned from the Messenger. Their influence was great, for through them the Prophet established family ties with the people of Khaybar (through Safiyya), the Banu Amir ibn Sa'sa'a (through Maymuna), the Banu Makhzum (through Umm Salama), the Umayyads (through Umm Habiba), and the Banu Mustaliq (through Juwayriya). The women of these tribes would come to their "representative" among the Prophet's household ask her about religious matters.
In the last year of his Messengership, the Messenger went to Makka for what has become known as the Farewell Pilgrimage. In his Farewell Sermon at 'Arafat to more than 100,000 people, he summarized his mission and told his audience: "Those who are here should convey my speech to those who are not."  Some time later, the last verse to be revealed commanded the Muslim community to practice and support Islam: Fear a day when you will be returned unto God and every soul shall be paid what it earned; they will not be wronged (2:281).
 Muslim, "Iman," 178; Bukhari, "Iman," 178.
 Muslim, "Iman," 182.
 Muslim, "Fada'il al-Sahaba," 161.
 Bukhari, "Tafsir," 98/1,2,3; Muslim, "Fada'il al-Sahaba," 122.
 Ibn Ma'ja, "Muqaddima," 17.
 Muhammad 'Ajjaj al-Khatib, "al-Sunna Qabl al-Tadwin," 160.
 Bukhari, "'Ilm," 9; Ibn Hanbal, 5:41.