1. On the authority of the Commander of the Faithful Abu Hafs Umer ibn al Khattab (may Allah be pleased with him), who said: I heard the Messenger of Allah (the blessing and peace of Allah be upon him) say:

" Actions are but by intention and every man shall have but that which he intended. Thus he whose migration was for Allah and His Messenger, his migration was for Allah and His Messenger, and he whose migration was to achieve some worldly benefit or to take some woman in marriage, his migration was for that for which he migrated." 

2. Also on the authority of Umar (may Alllah be pleased with him), who said: 

One day while we were sitting with the Messenger of Allah (may the blessings and peace of Allah be upon him) there appeared before us a man whose clothes were exceedingly white and whose hair was exceedingly black; no signs of journeying were to be seen on him and none of us knew him. He walked up and sat down by the Prophet (may the blessings and Peace be of Allah be upon him). Resting his knees against his and placing the palms of his hands on this thighs, he said: O Muhammed! tell me about Islam. The Messenger of Allah (may the blessings and Peace be of Allah be upon him) said : "Islam is to testify that there is no god but Allah and Muhammad is the Messenger of Allah, to perform the prayers, to pay the Zakat, to fast in Ramadan, and to make the pilgrimage to the House (Ka'aba) if you're able to do so". He said: you have spoken rightly, and we were amazed at him asking him and saying that he had spoken rightly. He said: Then tell me about Iman. He said : "It is to believe in Allah, His angles, His books, His messengers, and the Last Day, and to believe in divine destiny, both the good and the evil thereof". He said: you've spoken rightly. He said: then tell me about Ihsan. He said: " it is to worship Allah as though you are seeing Him , and while you see Him not yet truly He sees you." He said: then tell me about the Hour( the day of judgment). He said: "The one questioned about it known no better than the questioner." He said: Then tell me about its signs. He Said: that the slave-girl will give birth to her mistress and that you will see the barefooted, naked, destitute, herdsmen competing in constructing lofty buildings. Then he took himself off and I stayed for a time. Then he said: "O! Umer, do you know who the questioner was?" I said: Allah and His Messenger know best. He Said: "It was Gabriel, who came to you to teach you your religion" 

3.On the authority Abu Abd Ar-rahman Abdullah, the son of Umar ibn al Kattab (may Allah be pleased with them both), who said: I heard the Messenger of Allah (may the blessings and Peace be of Allah be upon him) say: 

"Islam has been built on five (Pillars): testifying that there is no god but Allah and that Muhammad is the Messenger of Allah, Performing the prayers, paying the Zakat, making the pilgrimage to the House(Ka'aba), and fasting in Ramadan."