What is the ruling on witnessing a marriage contract in exchange for a sum of money?

Scholars have differed regarding the permissibility of taking payment for bearing witness. The Maliki and Shafi'i schools of thought permit it for those who make it their profession to bear witness, citing common practice as their evidence. In contrast, the Hanafi school of thought prohibits it, reasoning that bearing witness is a communal obligation (fard kifayah) and that it is impermissible to take payment for an obligation. Based on the opinion of those who permit taking payment for bearing witness, there is no impediment for a witness to a marriage (nikah) to receive compensation for his testimony, especially if he has undertaken it as a profession.