Now i realise what you were talking about.
This is a weird one though. Like, pretty sure you technically couldn't just "sample" a busker.
Not keen on the use of the word "sample" here either, as technically you're making a recording. Fyi, if you recorded it... you own the copyright to the recording. But it's similar to using a session musician and not paying them. You have to pay (pr whatever was agreed) for the performance, and they'd be listed as a performer on the record.
But then, if you went into a public space and recorded ambient noise, is that fine? And what if copyrighted or other content is performed during that ambience? And I guess the question legally would come down to is the content of your recording really focussed on something specific. (In this case, the pastors speech).
It's akin to.. for example... say someone says "you're not allowed to take a photo of this" and you say you're taking a photo of the space around it, or someone who happens to be in front of it.
All that kind of messy trickery and details.