When are the words of a scholar – whether he was a Sahaabi or otherwise – regarded as binding evidence?

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Check below answers in case you are looking for other related questions:
A fabricated report about the Isra’ and Mi‘raaj
How can I verify the sources of the hadeeths quoted in the fatwas on the Islam Q&A website?

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Is it proven in the hadith that whoever kisses the Black Stone will be admitted to Paradise without being brought to account?
Is following da’eef hadeeths regarded as shirk?
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A fabricated report about the Isra’ and Mi‘raaj
How can I verify the sources of the hadeeths quoted in the fatwas on the Islam Q&A website?

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