I've found a reference to Pete Seeger singing a song with those lines on October 12th, 1969, a concert at Trinity College (source). The lyrics were reported to go "Here I am, here I'll stand, though I'm told it's stolen land. I've been too long a rover The time for stealing is over." According to the report, the song was an "enigmatic, unfinished closing song" to his set.

You can see an image of him performing on page 1 of the weekly edition of The Trinity Tripod (link), while the preceding week's paper noted that the concert ran from 3-5 PM in the Ferris Center (link).

I haven't been able to turn up anything else, but will keep looking. May be worthwhile to find and listen to as many live performances from 1969/1970 as you can to try and find it.