Hi Monika, it's from season 2 episode 22 ("For love or money")
I know that you've copied the photo link (http://rdanderson.com/photos/macgyver/1 ... 21-01x.jpg
) from the RDA gallery which has the subtitle "Prisoner of conscience" but I skipped through the episode and it's not. On the second of the similiar photos of the gallery you can see the knife in the balloon and then it hit me what episode it must be.
Here's the prove