4:136An-Nisaa

"The Messenger of Allah (ﷺ) said: 'No slave truly believes until he believes in four things: in Allah alone with no partner; that I am the Messenger of Allah; in the resurrection after death; and in the Divine Decree (Qadar).'"

"The Messenger of Allah said: 'Whoever has intercourse with a menstruating woman, or with a woman in her rear, or who goes to a fortuneteller and believes what he says, he has disbelieved in that which was revealed to Muhammad.'"

'A slave (of Allah) shall not believe until he believes in four: The testimony of La Ilaha Illallah, and that I am the Messenger of Allah whom He sent with the Truth, and he believes in the death, and he believes in the Resurrection after death, and he believes in Al-Qadar." Another chain reports a similar narration.

One day while Allah's Messenger (ﷺ) was sitting with the people, a man came to him walking and said, "O Allah's Messenger (ﷺ). What is Belief?" The Prophet (ﷺ) said, "Belief is to believe in Allah, His Angels, His Books, His Apostles, and the meeting with Him, and to believe in the Resurrection." The man asked, "O Allah's Messenger (ﷺ) What is Islam?" The Prophet (ﷺ) replied, "Islam is to worship Allah and not worship anything besides Him, to offer prayers perfectly, to pay the (compulsory) charity i.e. Zakat and to fast the month of Ramadan." The man again asked, "O Allah's Messenger (ﷺ) What is Ihsan (i.e. perfection or Benevolence)?" The Prophet (ﷺ) said, "Ihsan is to worship Allah as if you see Him, and if you do not achieve this state of devotion, then (take it for granted that) Allah sees you." The man further asked, "O Allah's Messenger (ﷺ) When will the Hour be established?" The Prophet (ﷺ) replied, "The one who is asked about it does not know more than the questioner does, but I will describe to you its portents. When the lady slave gives birth to her mistress, that will be of its portents; when the bare-footed naked people become the chiefs of the people, that will be of its portents. The Hour is one of five things which nobody knows except Allah. Verily, the knowledge of the Hour is with Allah (alone). He sends down the rain, and knows that which is in the wombs." (31.34) Then the man left. The Prophet (ﷺ) said, "Call him back to me." They went to call him back but could not see him. The Prophet (ﷺ) said, "That was Gabriel who came to teach the people their religion." (See Hadith No. 47 Vol 1)

"One day the Prophet (ﷺ) appeared among the people. A man came to him and said: 'O messenger of Allah, what is Iman (faith)?' He said: 'To believe in Allah, His angels, His books, His Messengers and the meeting with, and to believe in the Final Resurrection.' He said: 'O Messenger of Allah, what is Islam?' He said: 'To worship Allah (alone) and not to associate anything with Him; to establish the prescribed prayers, to pay the obligatory Zakat, and to fast Ramadan.' He said: 'O Messenger of Allah, what is Ihsan? He said: 'To worship Allah as if you see Him, for even though you do not see Him, He sees you.' He said: "O Messenger of Allah, when will the Hour be?' He said: 'The one who is being asked about it does not know more than the one who is asking. But I will tell you about its signs. When the slave woman gives birth to her mistress that is one of its signs. When the shepherds compete in constructing tall buildings that is one of its signs. And there are five things which no one knows except Allah.' Then the Messenger of Allah (ﷺ) recited the Verse: "Verily, Allah, with Him (Alone) is the knowledge of the Hour, He sends down the rain, and knows that which is in the wombs. No person knows what he will earn tomorrow, and no person knows in what land he will die. Verily, Allah is All-Knower, All-Aware (of things)."