1,196. A Lone Witness; A Paid Witness

181:13 The testimony of a lone witness is acceptable in monetary cases, since one witness can obligate a litigant to take an oath. A single witness is also acceptable concerning a matter of prohibition. If the prohibited thing has not yet been done, one may testify in order to keep people from sin. However, if the prohibited thing has already been done, a lone witness may not testify. Since a single witness isn't relied upon, doing so would only be considered slandering another person.

181:14 If a person accepts payment to testify, his testimony is invalid. It's only when one has witnessed an incident that he is obligated to testify for free. However, if they want him to go and see some matter and later testify regarding it, he is entitled to compensation. This compensation may only be commensurate with the effort involved, nothing more. Similarly, if it's an effort for one to appear before beis din, he may accept appropriate compensation for his trouble but not more.