ما هو الدليل من السنة والسلف على شرعية القياس، وهل صحيح أن أي حكم شرعي بني عليه باطل؟

The foundations of Islamic legislation are the Quran and the Sunnah only. Consensus (Ijma') and analogical deduction (Qiyas) are not independent sources of legislation; rather, they are means of establishing jurisprudential rulings based on the texts of revelation. Imam Al-Shinqiti, in "Adhwa' al-Bayan," refuted the Zahiris who deny Qiyas, explaining that Qiyas is of two types: a corrupt type that is not valid, and a sound type that does not contradict a text. He gave examples for this, such as the Prophet's prohibition of judging while angry, upon which Al-Shinqiti analogized everything that disturbs one's thought. He also exemplified with the prescribed punishment for slandering chaste women, upon which he analogized the punishment for slandering chaste men. And the Prophet's prohibition of urinating in stagnant water, upon which he analogized everything that pollutes it. And his prohibition of sacrificing a one-eyed animal, upon which he analogized a blind animal. He clarified that the Zahiris ignore the meanings of legislation and the interests upon which the rulings are built.