Basis from Hadiths:
When the Messenger of Allah (ﷺ) intended to send Mu'adh ibn Jabal to the Yemen, he asked: How will you judge when the occasion of deciding a case arises? He replied: I shall judge in accordance with Allah's Book. He asked: (What will you do) if you do not find any guidance in Allah's Book? He replied: (I shall act) in accordance with the Sunnah of the Messenger of Allah (ﷺ). He asked: (What will you do) if you do not find any guidance in the Sunnah of the Messenger of Allah (ﷺ) and in Allah's Book? He replied: I shall do my best to form an opinion and I shall spare no effort. The Messenger of Allah (ﷺ) then patted him on the breast and said: Praise be to Allah Who has helped the messenger of the Messenger of Allah to find something which pleases the Messenger of Allah.
Analogical reasoning or qiyas is the fourth source of Islamic law-making, the use of which has been justified by both the Qur’an and the Prophet (pbuh).
There are three elements necessary to make a sound analogy, using the Qur’an and Hadith, which are:
By relating these together, it is possible to arrive at a new judgment, the hukm. An example that could be given by candidates is:
It is important that the asl must always be from the Qur’an or the Sunna of the Prophet (pbuh) or by ijma.
An example from the Hadith that could be given is:
The Prophet (pbuh) said: ‘Every intoxicant is khamr (wine) and every intoxicant is forbidden.’ (Abu Daud)