We ought to point out here to the fact that the Shi`as have always insisted that the sources of the Shari`a must be: the Book of Allah and the Sunnah of His Prophet, adding nothing to them due to their conviction that there are sufficient texts with their Imams relevant to all problems for which people seek solutions. 

One may find it strange, maybe even highly unlikely, that the Imams from Ahl al-Bayt have texts that satisfy all the needs of people across all centuries and till the Hour. In order to make this fact clear to the reader, we have to point out to the following: 

If a Muslim is convinced that Allah, Glory to Him, sent Muhammad a legislative system (Shari`a) which complements all previous systems and overwhelms them in order to complete the human march on this earth so that it may be prepared for the eternal life hereafter, 

Based on this verse, there is nothing excluded from the Book of Allah, the most Exalted One, yet man, due to his limited mentality, cannot realize all the things which Allah, Glory and Exaltation to Him, has stated because of a great wisdom which only people of knowledge realize. For example, the most Glorified and Exalted One says, "There is not a single thing which does not glorify Him with His praise, but you do not understand [the method of] their glorification" (Holy Qur'an, 17:44). 

The phrase "There is not a single thing" does not exclude anything at all and is indicative of the fact that mankind, animals, and even inanimate objects celebrate the praise of Allah. Man may comprehend how animals and living beings, including plants, celebrate the praise of their Maker, but his mind may not be able to comprehend how rocks, for example, can also do so, yet the Almighty has already said, "Surely We made the mountains sing the glory (of Allah) in unison with him in the evening and at sunrise" (Holy Qur'an, 38:18). 

If we accept all the above and believe in it, we will have to accept and believe that the Book of Allah contains all injunctions which people need till the Day of Judgment, but we simply do not realize them except when we refer to the one to whom that Book was revealed and who comprehended all the meanings it contains, namely the Messenger of Allah. The most Exalted One has said, "We have revealed the Book to you clearly explaining everything and guidance, mercy, and glad tidings for those who submit" (Holy Qur'an, 16:89). 

If we believe that Allah, Glory to Him, has clarified everything for His Messenger so that he may explain to people what revelation has been sent to them, we will have to believe that the Messenger of Allah has clarified everything, leaving nothing needed by people till the Day of Judgment without giving a ruling in its regard. 

If such a clarification has not reached us, or if we do not now know it, then this is only the outcome of our own shortcoming, negligence and ignorance, or it may be the outcome of the deficiency of the means linking us to it, or it may have resulted from the ignorance of the companions and their lack of awareness of what he had clarified. 

But Allah, Glory and Exaltation are His, is too wise to ignore the fact that all these are possibilities, or even realities, so He does not let His Shari`a suffer loss; therefore, He chose from His servants certain Imams whom He permitted to inherit the knowledge of His Book and the ability to explain it to others so that people may not have an argument against Allah; He has said, "Then We gave the Book for an inheritance to those whom We chose from Our servants" (Holy Qur'an, 35:32). 

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. Allah has said, "Surely Allah chose Adam and Noah and the descendants of Abraham and the Descendants of Imran above the nations" (Holy Qur'an, 3:33). The Imams whom Allah selected to conclude His Messages with that of Muhammad are the Imams of guidance from the Prophet's Progeny, and they have all descended from Abraham, one progeny descending from another, and they are the ones to whom he referred when he said, "The caliphs after me are twelve: all of them are from Quraysh."[120] 

For every age and time there is an imam, so "Whoever dies without knowing who the Imam of his time is dies the death of jahiliyya," as another tradition says. When Allah, Glory and Praise are due to Him, chooses an Imam, He purifies him and protects him against sinning or erring and teaches him; He surely does not bestow wisdom except upon those who deserve it and are worthy of it. 

If we go back to the basis of the subject-matter, which is the Imam knowing all what people need of the injunctions of the Shari`a from the texts available in the Book of Allah and the Sunnah, and which are suitable for mankind's progress till the time of the Hour, we will not find anyone in the Islamic nation claiming to be as such other than the Imams of Ahl al-Bayt who declared the same quite often, saying that with them is the saheefa jami`a which was dictated by the Messenger of Allah and written down in the handwriting of Ali ibn Abu Talib, and that it contains everything people need till the Day of Judgment, including the penalty for slightly scratching one's cheek. We have already referred to this saheefa jami`a which used to be carried by Ali with him and to which al-Bukhari and Muslim have referred, each in his own Sahih book, and not even one Muslim can say that this is not true. 

Based upon the above, the Shi`as who restricted their loyalty to the Imams of Ahl al-Bayt have always issued their juristic rulings according to the texts of the Holy Qur'an and the Sunnah without resorting to any other source, at least during the Twelve Imams' three generations. As for "Ahl al-Sunnah wal Jama`ah," these were forced to resort to ijtihad and qiyas and other things because of the loss of hadith and because of their Imams' ignorance thereof since the days of the first period of caliphate. 

If their caliphs deliberately burned the Prophet's ahadith and prohibited their circulation and dissemination, and if their most prominent one says, "The Book of Allah suffices us," thus discarding the Prophet's Sunnah, it is quite natural that they lack the texts which explain the injunctions embedded in the Holy Qur'an. We all know that apparent Qur'anic injunctions are very few in number. They, generally speaking, need the explanations provided for them by the Prophet. This is why we read the following verse in the Holy Qur'an: "And We have revealed to you the Reminder so that you may clarify for men what has been revealed to them" (Holy Qur'an, 16:44). Because the pillars of "Ahl al-Sunnah wal Jama`ah" burnt the Sunnah which explained the Holy Qur'an, thus losing the texts that explained the Holy Qur'an or even the Sunnah itself, they had no choice, since the case is as such, except to resort to their own personal views, to analogy, and to consulting their scholars to select what the latter liked, and what served their own temporal interests. It is quite natural, then, that they have always needed all of that in the absence of such texts; they resort to all such means only due to their dire need.