Prophets were sent to serve as examples who must be followed consciously. After mentioning the Prophets in Surat al-An'am, God told His last Messenger: Those are they whom God has guided, so follow their guidance (6:90). In particular, we are told to follow Muhammad's example: You have a good example in God's Messenger for whoever hopes for God and the Last Day, and remembers God oft (33:21).
God's Messenger is our leader. Just as we pray as he prayed, we must exert ourselves to live as he lived. Those who followed him during the first Islamic century were real representatives of the true Islamic life. God's Messenger says of them:
Muslim armies will arrive, after me, at the gates of cities. They will be asked: "Did any of you see the Prophet?" The answer will be affirmative, and the gates will be opened for them. Those who succeed them also will perform jihad and be asked: "Did any of you see those who saw the Prophet?" They will reply in the affirmative, and the cities will be conquered by them. As for the third generation, its members will be asked: "Did any of you see those who saw the followers of the Prophet's Companions?" When this question is answered in the affirmative, their conquest will be successful. 
In another narration by Bukhari and Muslim, God's Messenger says: "The best of you are those who live in my period, then those who succeed them, and then those who follow them." 
Those three generations strictly followed the Prophet and, accordingly, were granted great victories throughout the world. Jesus had predicted them, saying: "The banners of the holy ones are in their hands."  These holy ones are the Companions of Muhammad and those who follow his way in every century.
In a Tradition, although with a weak chain of transmission, God's Messenger declares: "The pious scholars of my nation resemble the Prophets of the Children of Israel."  'Umar submitted himself to God so sincerely that, as a servant of God, he was far more effective than had been expected. During his caliphate, Iran, Iraq, and Egypt were conquered. Muslim armies marched throughout a vast area, led by such great commanders as Abu 'Ubayda ibn al-Jarrah, Shurahbil ibn Hasana, Sa'd ibn Abi Waqqas, 'Amr ibn al-'As, and Yazid ibn Abi Sufyan.
Jerusalem was conquered during his caliphate. When the Muslims' supreme commander asked its priests to submit the keys of the city, they answered: "We cannot see among you the man to whom we are to submit the keys." They had read in their religious books a description of who was qualified to receive the keys.
So the priests and Muslim commanders waited while 'Umar and his servant were riding a camel, by turns, toward Jerusalem. Although 'Umar ruled over lands twenty times the size of Turkey, he did not own a camel. He borrowed one from the state treasury and set out with his servant. When they approached the river Jordan, his waiting commanders on the river's other side were excited, praying: "O God, let 'Umar be the one riding when they reach the river, for these Romans are fond of pomp and display. They may not esteem us if they see the caliph pulling a camel ridden by a servant." But God had destined the latter scenario. When 'Umar approached, the priests noticed, among other things, several patches on his robe. This was the man described in their books, and so they gave him the keys of Jerusalem.
'Umar never deviated from the path of God's Messenger. While on his deathbed, after being fatally stabbed by a Magian slave, he refused food and water because he was too weak. However, he always prayed when it was time to do so, even if it caused his wounds to bleed. He would say: "Those who don't pray have nothing to do with Islam." An exemplary follower of God's Messenger, his own example would be followed by succeeding generations.
 Bukhari, ibid., 1; Muslim, ibid., 212.
 Ibrahim al-Halabi, Sira, 1:218.
 Ajluni, Kashf al-Khafa', 2:83.