This is a close (although not word-for-word literal) translation:
Although might pass-by both winter and spring,
and summer days fade, and the year expire,
but surely you will return to me, I am certain;
and I shall be waiting as I once promised.
God guard you, wherever in the world you may roam,
God comfort you, if now at his footstool you stand;
Here shall I wait until you come back,
and if you wait on high, I’ll meet you there, my friend.