The Qur'an says : "O ye who believe! Obey Allah and obey the Messenger and those who are men of authority among you and if you have a dispute concerning any matter, refer it to Allah (His Book) and the Messenger (His Sunnah) believe they say 'should we believe as foolish believe'? (Surah : Al-Baqarah, V : 13). And if they believe in the like of that which you believe, then they would be rightly guided (Surah Al-Baqarah, V:137).
As regards the Consensus of the Ummah (Ijma), the Qur'an says, "And whosoever opposes the Prophet (PBUH) after guidance (of Allah) has been made clear to him and chooses to follow a path other than that of the belivers, than we send him that unto which he himself has turned and expose him onto the path of hell, a hopeless journey's end" (Surah : Al-Baqarah, V:115).
So it is necessary for the Ummah to follow the path adopted by the believers and thus continue the chain up to the last day.
And if a solution for new issue is not found in the book, or in the Sunnah of the Prophet (PBUH) nor in the practice of the companions, then the scholars of the time should examine the issue and arrive at an opinion by applying Qiyaas (analogy). In this field, the Ummah aknowledges the four schools of thought. The Prophet (PBUH) approved this method of applying anology to seek answers.
The Prophet (PBUH) of Islam guided Muaadh, one of His companions, to apply analogy if an answer was not directly available on an issue in either the Book or the Sunnah. Hadrat Umar (RA), during his time, commanded that the findings of the early scholars should be given preference over one's own deductions. Only the qualified scholars (theorists) of Islam have the right to apply analogy and draw conclusions, not the lay persons.