How does a Muslim deal with a Hadith that some scholars have authenticated while others have deemed it weak? Should one act upon it? Does the multiplicity of narrations for the wordings of a Hadith mean that one of them is authentic?

The matter in the science of Hadith (definition) is like any other science: whoever is capable of preferring one opinion over another and possesses the tools of this art, let him follow what appears to him to be more sound. And whoever is not capable, then he must imitate someone whose knowledge and religiosity are trusted. If scholars agree on the authenticity of a Hadith, then it is an undeniable proof. If they differ, then the individual should imitate someone whose knowledge and religiosity are trusted. As for the differing narrations of a single Hadith, it is possible that the Prophet, peace and blessings be upon him, said both wordings, or that one of the narrators narrated by meaning. In such a case, one resorts to preferring based on greater number of narrators or better memorization. The Hadith scholars and commentators explain the probabilities involved.