system
Given the following post, respond as if you're commenting on Reddit:
human
How large does an object in space need to be in order to gravitationally bind an average human to its surface?
gpt
"Bind an average human" seems to be the crux of your question.

Lets instead ask "Whats the biggest object a human can escape the gravitational pull of?"

For this we need 2 items: the escape velocity of an object, and the average speed a human can reach.

A small amount of googling tells me that the average jumping height for males is about .504 meters, while a good height is .6. Lets use .5 for a simple answer.
Using basic kinematics, we find that humans can generally give themselves a velocity of sqrt(g) or about 3.13 m/s.
However, this is only vertically. Humans are generally able to sprint at a speed of around 7 m/s. So it will be much easier for our astronaut to simply start sprinting then it would to be jumping.

The escape velocity of a body is given by v=sqrt(2*G*M/r). So big objects are hard to get away from, but large objects are easy to get away from. So density comes into play. This won't be as easy as giving a simple number.

Instead, lets find some likely candidates. Ceres is the largest asteroid in our solar system. Ceres has a mean radius of 473,000m and a mass of 9.4*10^20 kg.
This gives Ceres an escape velocity of 515 m/s. No, chance of getting off that.

67P/Churyumov–Gerasimenko is the comet that was recently landed on by Rosetta's Lander Philae, which famously bounced but stayed on the surface. Because of its odd shape, we can get about 4100 meters away from its center. It has a mass of 9.98*10^12 kg. So it has an escape velocity of around .5 m/s at its tip! We can definitely escape this!

So we're looking somewhere between our solar system's biggest asteroid and an oddly shaped comet.