That was his precum from his dick. Also, some people can actually 'self-lubricate' from their ass. It is a lubricative film that the ass produce to help push feces through the rectum. You can look it up. It's rare but not that dangerous unless there's actual complications, if I'm not mistaken.
If any guy outside of omegaverse is wet....go to the hospital. There is a big issue here. (⊙…⊙ )