Jambo hufafanuliwa kuwa chanzo katika Usul pale linapotumika kama chanzo cha Ahkam (hukumu) mpya. Qiyas ni chanzo kwa sababu tunaweza kutoa Ahkam mpya kutokana nayo. Kwa kulipanua hukumu ya asili kwenye hali mpya kupitia 'Illah inayofanana, tunapata Ahkam mpya kwa mambo mapya, na hivyo Qiyas ni chanzo. Hii ni mojawapo ya njia tunazoweza kutambua uwezo wa Uislamu wa kutumika katika kila zama na kila mahali, kwani Ahkam zinaweza kupatikana kwa hali mpya na matatizo mapya.

Something is defined as a source in Usul when it serves as a source for new Ahkam (rules). Qiyas is a source because we can extract new Ahkam from it. By extending the original rule to new realities via a shared „Illah, leads to new Ahkam for new realities and hence Qiyas is a source. This is one of the ways we can appreciate the capacity of Islam to apply to all times and places as Ahkam can be deduced for new realities and problems.

Qiyasi daima hujengwa juu ya nguzo nne zifuatazo:

Qiyas is always built on the following four pillars:

i. Asl (jambo la kale).

i. Asl (old matter).