The idea of limits is that when we take a concept to infinity, we can see the point to which we would approach, even if in practice we could never get there. As the number of sides of a polygon tends towards infinity, we reach a circle that itself is not a polygon, being a smooth line.
The righteous stand in a similar relation to the shechinah in this teaching of Raba, being described as lamps that burn and shed light over the world. But if we take the concept of a lamp to its greatest limit we reach the idea of a torch that is not itself a lamp, but is the limit implied by the small flames of all the lamps.
Thus the righteous point the way towards God, shed a kind of divine light on the universe, even though when compared to the divine light of the shechinah (the feminine presence of God) they are like candles in the daytime.
