In a metaphorical sense, the mitzvot are the limbs of God.
And so when a person performs a mitzvah, he himself constitutes, as it were, a limb of God acting within existence.
When a person gives charity, he is the hand of God “satisfying the will of every living being.”
With every mitzvah, he causes God to dwell in the world.
He makes a portion of the world a part of God, as it were–a limb of the Holy One, blessed be He.
–Rabbi Adin Steinsaltz