A stiffnecked people. This epithet, which becomes epitheton usitatum, is here used for the first time. It does not so much mean "obstinate" as "perverse" like a horse that stiffens the neck when the driver pulls the right or left rein, and will not go the way he is wanted to go.
(Compare Exodus 33:3, Exodus 33:5; Exodus 34:9; Deuteronomy 9:6, Deuteronomy 9:13; Deuteronomy 31:27; etc.