Why does it say that "Mekor Chayim" is with Hashem?
Radak: It is like [spring] water from a source; it never ceases, the way gathered water ceases. So life in the world to come never ceases. This is the life that is not followed by death, the light that is not followed by darkness.
Malbim: Spiritual life is true life, from the source (Hashem) - "v'Atem ha'Devekim ba'Shem Elokeichem Chayim Kulchem ha'Yom" (Devarim 4:4). Physical life is a mere conduit that flows from it. Mitzvos are ladders from which one can draw from the source of life; sins are true death and darkness - surely one should hate them!
What do we learn from "b'Orcha Nir'eh Ohr"?
Malbim: Physical light is a mere spark of the true Ohr - Divine spiritual light. Just like sight is only via light, physical light is seen only via the supreme light.
Mishnas R. Aharon (4, p.36): From what we understood in Torah, we will see that there is more light, and we will hope to attain it. A parable is one who enters the king's treasure room, and he sees a door to a more internal room, and he wants to enter it, and from there he sees more internal rooms.
