In the first stanza of "Man," the speaker claims that no one would built a stately (grand or impressive) house unless he intended to live there. Since God created the Earth and "man" (humans), God must have intended to live there: in the heart and consciousness of each person and/or as a spiritual presence in the world.
In the second stanza, the speaker notes that man (humanity) is this stately house because man is everything:
For man is ev'ry thing,
And more; he is a tree, yet bears more fruit;
A beast, yet is, or should be, more;
Reason and speech we only bring;
Parrots may thank us if they are not mute,
They go upon the score.
Man bears similar traits and characteristics to other things in the world except man surpasses those other things. In this sense, man is a microcosm of the world; the condensed paradigm of the world's proportions.
Although the poem is an homage to God, it is also an anthropocentric poem in that it focuses on man as the center of the world. Man's proportions are symmetrical and all of his parts have private amity (work well together). The next four to five stanzas describe the ways in which the world exists to serve man. "Herbs gladly cure our flesh," "For us the winds do blow," and "The stars have us to bed;" -- all of these examples indicate that these are "servants" that wait on man, some of which he (we) do not even notice.
In the eighth stanza, the last two lines symbolize the idea that man is a microcosm of the larger world:
O mighty love! Man is one world, and hath
Another to attend him.
In the last stanza, the speaker invites God to dwell in the world (be a spiritual guide to man) so that man my dwell with God in the afterlife ("That it may dwell with thee at last!"). The last two lines express the relationship between man and God; as God made the world to serve mankind, the world of mankind will serve God.