Is prayer valid when performed behind a scholar belonging to a different school of law regarding subsidiary issues (Furu')?

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Prayer behind those who hold differing opinions in subsidiary jurisprudence, such as the followers of Abu Hanifa, Malik, and Al-Shafi'i, is valid and not disliked. Imam Ahmad affirmed this. The basis for this ruling is that the Companions and the Successors, and those after them, habitually prayed behind one another despite their differences in subsidiary matters, which constitutes a consensus (*ijma'*). Furthermore, the differing jurist is either correct in his independent reasoning (*ijtihad*), thus deserving two rewards (one for reasoning and one for correctness), or he is mistaken, in which case he still receives a reward for his reasoning, and error is forgiven from him. Even if the Imam neglects a pillar or condition that the follower believes is required, the apparent view of Imam Ahmad supports the validity of praying behind him. This is supported by the precedent where Imam Ahmad permitted praying behind someone who wore tanned animal hides, provided the person held an interpretation that tanning purifies them, based on the saying, 'Any hide that has been tanned has become pure.'