What is the origin of the concept of four ways to follow Islam?

Sources

• ✓ Sahih al-Bukhari 2:1

  Sunni SAHIH

  Sahih al-Bukhari · Book 2, Hadith 1 · Narrated by Ibn Umar

  The Messenger of God, peace be upon him, said: 'Islam is built upon five pillars: the testimony that there is no god but God and that Muhammad is the Messenger of God; establishing prayer; giving alms; pilgrimage to the House; and fasting during Ramadan.'

• ✓ Al-Kafi 1:44

  Shia

  Al-Kafi · Book 1, Hadith 44

  Islam is built upon five: prayer, almsgiving, fasting, pilgrimage, and allegiance (wilayah). Nothing was called out to like allegiance. People accepted four and left this one — namely, allegiance. — OR — He said: Drink from the whey of a menstruating woman but do not perform ablution with it. — OR — It is enough sin for a person to neglect those he supports. — OR — I heard Abu Abdullah (peace be upon him) say: My father (peace be upon him) used to say that war has two rulings. If the war is ongoing and its burdens not yet lifted, and its people not yet overwhelmed, every captive taken under those conditions is at the Imam’s discretion: he may kill him or amputate his hand and foot alternately without killing, and leave him to bleed until he dies. This is in line with God's word: "The recompense of those who wage war against God and His Messenger and strive to cause corruption in the land is that they be killed or crucified, or their hands and feet cut off alternately, or be exiled from the land." The chosen Imam is appointed over one matter: disbelievers; not over different matters. I said to Abu Abdullah: God's words "or be exiled from the land" — he said: "That means to chase them with horses until they flee; if captured by horses, their judgment is as described; the other ruling applies when the war ends its burdens and the enemy is overwhelmed; then every captive is in their hands, and the Imam may pardon them, release them, or enslave them." — OR — I asked Abu Ja'far about the phrase of God, the Exalted, "Created and not created." He said, "The created are the spirits whom God created in the loins of Adam (peace be upon him). He took from them a covenant and then placed them in the loins of men and wombs of women. They are the ones who come forth into the world until they are questioned about the covenant. As for the not created, they are every soul not created in the loins of Adam when the spirits were created and given the covenant. They are the sperm from miscarriage and abortion before the soul, life, and permanence are breathed into it." — OR — He told the owner of the will that he may revise it and add to it as long as he is alive. — OR — I asked him about the saying of Allah, the Exalted: 'And He sent against them birds in flocks, striking them with stones of baked clay.' He said: 'There was a flock of birds coming to them from the direction of the sea. Their heads were like the heads of wild beasts, and their claws resembled the claws of wild beasts. Each bird had three stones: two stones on its feet and one stone in its beak. They began to cast these stones until the bodies of the enemy were coated with them, killing them. Before that day, no one had seen the disease known as smallpox nor seen such birds before or after that day.' He added: 'Whoever escaped that day fled until he reached Hadhramaut, a valley below Yemen. Then Allah sent a flood upon them and drowned them all. It is said that no water had been seen in that valley for fifteen years before that day. Because they died there, it was named Hadhramaut.'