In the Newtonian theory, gravity is instantaneous. This is because the force law says that whenever you have two objects a distance $r$ apart, there will be a force between them inversely proportional to $r^2$. The force at any given instant depends on the distance at that same instant, which means that if you move one of the bodies a little bit, the other one will know about it immediately.
Of course, this is not what actually happens. It's just what you can deduce from Newtonian mechanics.
