In "A Valediction: Forbidding Mourning," what is the meaning of the line, "Such wilt thou be to me, who must Like th' other foot, obliquely run"?

This line, that comes at the end of the poem, concludes the
conceit, or elaborate metaphor, that Donne employs in this remarkable poem to describe the
relationship of a union of souls so complete that distance cannot separate them. Note that the
whole poem is addressed to the speaker's wife, in which the speaker urges her to not mourn open
and visibly. After these initial recommendations, the speaker explains how they are connected so
closely and how this connection will not break through death.

The
speaker therefore compares their "two souls" to a pair of compasses, that are really not two
separate objects, but one object made up of two parts, just as the speaker and his wife are. In
an image that is remarkable for its beauty the speaker justifies his comparison to himself and
his wife as a pair of compasses:

readability="29">

If they be two, they are two
so

As stiff twin compasses are two,

Thy
soul the fixed foot, makes no show

to move, but doth, if th'other
do.

And though it in the centre
sit,

Yet when the other far doth
roam,

It leans, and hearkens after
it,

And grows erect, as that comes
home.

It is in this way, the speaker
affirms in the quote you have identified, that the wife will stay "still" as her husband ventures
off into the unknown, giving him the stability that he needs to chart his course and will keep
them "joined" no matter where the husband is voyaging.