Joe Heaney's text is transcribed in the MacColl/Seeger interviews at Musical Traditions:

Joe Heaney: Interview transcript - part 8: The Remaining Songs

Scroll down nearly to the bottom of the page. I don't think I've heard Heaney's rendition, but Alec Foster of Belfast had a similar set, including Melchisedec (Hugh Shields (rec) Folk Ballads from Derry and Donegal, Leader LEA 4055, 1972).

I ought to have said a rather than the relevant passage, since, as Brian's link shows, the man also appears in Genesis and (briefly) in Psalms.