To swear an oath by Jerusalem is to invoke God, seeing as he has chosen the city of Jerusalem as the place for his temple (Psalm 48:2; Matthew 4:5; Matthew 27:53). God is witness to your oath when you swear by Jerusalem, it is not a lesser oath that you are not obligated to keep.
35 ni par la terre, parce que c'est son marchepied; ni par Jérusalem, parce que c'est la ville du grand roi.