The Messenger of Allah has...

The Messenger of Allah has, indeed, explained to people everything they need and selected Ali to be his successor whom he taught everything people will need after his demise till the Hour due to the merits which Ali enjoyed over all other companions: very sharp intelligence, keen understanding, excellent memory, clear retention of what he hears.

The Prophet, therefore, taught him everything he knew and guided the nation to him, telling it that Ali is the gate from which his knowledge can be reached. If someone were to say that the Messenger of Allah was sent by Allah for all mankind, so he had no right to choose one particular person to teach while depriving all the rest, we would say that the Messenger of Allah had nothing to do with that; rather, he was a servant of Allah who received and carried out his Lord's inspiration.

Allah is the One Who ordered him to do so. Islam is the religion of unity and is based on unitarianism regarding everything; so, people have to be united and gathered under one leadership. This is a matter of simple common sense regulated by the Book of Allah and necessitated by reason and sentiment.

Allah Almighty has said, “Had there been many gods in them, they would surely have become in a state of disarray” (Holy Qur'an, 21:22) , and also “Never was with Him any (other) god: in that case, each god would certainly have taken away what he created, and some of them would certainly have overpowered others” (Holy Qur'an, 23:91) . Likewise, had Allah sent two messengers spontaneously, people would have been divided into two nations. Two parties, one opposing the other, would have resulted.

The Almighty has said, “And there is no nation except that a warner has gone among them” (Holy Qur'an, 35:24) . This is why every prophet left behind him a successor among his people and nation to protect them against dissension. This, by my life, is quite natural; all people know it, be they scholars or illiterate, believers or unbelievers.

Have you not seen how each tribe, party, or state has to have only one single president to preside over it and lead it, and two president cannot be followed simultaneously? Because of all the above, Allah, Glory to Him, selected from the angels carriers of His Message, and likewise from the people, granting them the honor of bearing the responsibility of leading His servants to Him, making them Imams guiding others according to His commandments.