Clearance needed for video on internet
 

Hi everyone--I'm making a documentary and I would like to incorporate a portion of a video that is posted on the internet (it is basically an informational video for a religion) as in it several key references are made pertinent to my film. Is it necessary for me to gain permission to use this video in my film? I'm guessing yes. Should I simply contact the copyright holder and get permission from them? And if so, what sort of contract is necessary for this kind of use? Thanks!

Peter