The first instance is in the third line of the second verse: "Still the captives long for freedom," sung to this phrase from the tune "Beach Spring":
"Freedom" is sung to the notes G F D.
Later in the second verse, there's the line "Healed the sick and freed the soul," sung to this musical phrase:
"Freed" is sung to the notes A G.
Finally, at the end of the fourth verse, there are the lines "That Your servants, Lord, in freedom / May Your mercy know and live." The first of these two lines is sung to this phrase:
Here, "freedom" is again sung to the notes G F D.