R' Manis Friedman, a popular Lubavitcher public speaker, likes to tell of his
night-long dialogue with a non-Chassidic kollel guy about whether Hashem needs us,
whether we need to have rachmanus on Him for making Himself
vulnerable to our freedom of choice. The kollel guy says Hashem is
perfect, how He can need anything?!
MF says, needing a mitzva is not an imperfection. But let's say it is.
What would you prefer that Hashem is perfect or that Hashem needs
you?
Kollel
guy said, that He's perfect.
MF
asks, why do you need Him to be perfect?
Kollel
guy says, because if He's not perfect, I won't serve him.
MF says,
if you're right that Hashem doesn't need anything, what does it mean
ivdu es Hashem – what kind of service can you do?
Kollel
guy said that's the one thing I never understood ... By
telling me that Hashem needs my mitzva, you're turning me off. If He
needs it, let Him do it!
Mf: If
you did not need anything, you wouldn't be a human being. To say
that Hashem needs, makes people uncomfortable because our needs are
seen as weaknesses.
Yes,
there are needs that are weaknesses like eating and sleeping, but a
need like friendship makes us human. If Hashem needs something, that
makes Him a living G-d.
*****
Just because the Kollel guy never came up with an answer for what it means to serve Hashem, doesn't mean there isn't an answer that doesn't require G-d needing something. In Chovos Ha'Levavos, written by a Rishon, there is an entire section on the Service of G-d - Shaar Avodas Ha'Elokim.
In it (in the edition with R' Avigdor Miller's commentary, p. 66, 72), it says the definition of avoda is
the feeling of humility of someone who receives a benefit.
What can we do for Hashem? Nothing, because Hashem does not need anything. But one thing we can do for Him is make something out of ourselves. How do we do this? By working to show our gratitude for what He does for us. Avoda is the service of Hashem that comes from a feeling of gratitude.
We contemplate His greatness, His wisdom, and everything He has done for us. It includes thinking of all the things He does in the world that reveal His presence. All the mitzvos of the Torah are only an introduction to this career of avoda.