The first line is "They that drink shall live forever," sung to this musical phrase from the tune "Naar mit öie":
The "forever" is sung with a melisma (F# E F# D); since it's drawn out, there's a musical sense of duration.
In writing this post, I noticed that those particular notes form a cross inscription, which is also repeated in the third phrase of the tune. I think the only connection between it and the text appears in the third phrase of the third verse: "Here the guilty [may find] free remission." "Remission" is sung to this cross inscription, and it is Jesus' death on the cross that provides us this "remission."
