What is the ruling on one who believes that evidence is a condition for issuing a fatwa, and describes those who accept a fatwa without evidence as being among those who have "taken their rabbis and monks as lords besides Allah"? Is this considered an act of disbelief, even though he has not declared those Muslims to be disbelievers?

A fatwa is an informing of the inquirer about the religious ruling concerning a specific issue. It must be based on a legitimate religious proof from the Quran, Sunnah, Ijma' (consensus), or Qiyas (analogy). Imams and scholars may differ in establishing a ruling due to their differences regarding the authenticity of the proof or the way it is deduced, but no Imam deliberately contradicts a proof.

Shaykh al-Islam Ibn Taymiyyah mentioned that the Imams agree on the obligation of following the Messenger of Allah, peace and blessings be upon him, and that everyone’s sayings can be accepted or rejected except for the Messenger of Allah, peace and blessings be upon him. If one of them has a saying that contradicts an authentic hadith, he has one of three excuses: he did not believe that the Prophet, peace and blessings be upon him, said it; or he did not believe that the issue in question was intended by that saying; or he believed that the ruling was abrogated.

When a proof becomes clear, it is obligatory to follow it, and it is not permissible to deviate from it. There is no excuse for anyone to follow an opinion that he knows is contrary to the proof. Whoever does so has incurred a share of the blame mentioned in Allah’s saying: (They have taken their scholars and monks as lords besides Allah) [Quran 9:31]. However, this might not constitute kufr (disbelief) due to the presence of a preventative factor or the absence of a condition. Shaykh al-Islam Ibn Taymiyyah stated that blame is incurred by whoever has the truth made clear to him and then abandons it, or is negligent in seeking it, or turns away from it due to caprice or laziness.

The mufti is not obliged to show the proof to the inquirer, but it is preferable to do so if the proof is something that the inquirer’s intellect can grasp.