Everyone loves a great sample but if you’re using a sample that is not from one of your own tracks you need to make sure they are legally cleared for use. This would involve getting the permission of all copyright owners and it applies to all samples, no matter how short it is!
If ever you're in doubt, or you're unable to ask the copyright owner (i.e. the person/s who own the publishing to the song), it's best to leave the sample out to avoid getting into any legal trouble later on.