The second hadith of book Arba’een an Nawawiya explains about Islam, iman and ihsan. This long hadith is one of main hadith that explains Islamic creed.
‘Umar (may Allah blesses him) said:
“While we were one day sitting with the Messenger of Allah ﷺ, there appeared before us a man dressed in extremely white clothes and with very black hair. No traces of journeying were visible on him, and none of us knew him. He sat down close by the Prophet ﷺ, rested his knee against his thighs, and said, “O Muhammad! Inform me about Islam”.
The Messenger of Allah ﷺ said, “Islam is that you should testify that there is no deity except Allah and that Muhammad is His Messenger. Then, you should perform salah. Pay the Zakah. Fast during Ramadan. And, perform Hajj to the House, if you are able to do so”.
The man said, “You have spoken truly”. We were astonished at his questioning him (the Messenger) and telling him that he was right.
But he went on to say, “Inform me about iman”.
He (the Messenger of Allah) answered, “It is that you believe in Allah and His angels, and His Books, and His Messengers and in the Last Day. Also in qadar (fate), both in its good and in its evil aspects”. He said, “You have spoken truly”.
Then he said, “Then, inform me about Ihsan!”.
He (the Messenger of Allah) answered, “It is that you should serve Allah as though you could see Him, for though you cannot see Him yet (know that) He sees you”.
He said, “Also inform me about the Hereafter”. He (the Messenger of Allah) said, “About that, the one questioned knows no more than the questioner.” So he said, “Well, inform me about the signs thereof.”
He said, “They are that the slave-girl will give birth to her mistress. Also you will see the barefooted, naked, destitute, the herdsmen of the sheep (competing with each other) in raising lofty buildings”.
Thereupon the man went of. I waited a while, and then he (the Messenger of Allah) said, “O Umar, do you know who that questioner was?”. I replied, “Allah and His Messenger know better.” He said, “That was Jibril (the Angel Gabriel). He came to teach you your religion”.[Narrated by Muslim].
This hadith includes within it all outwardly actions and inwardly beliefs. The sciences of the Sharia’ return back to this hadith due to it encompassing knowledge of the Sunnah. Hence, some of the scholars have termed this hadith the Mother or Core of the Sunnah, just as Surah al-Fatiha has been termed the Mother or Core of the Qur’an, due to it containing the entire Message of the Qur’an.