They have turned aside quickly out of the way which I commanded them: they have made them a molten calf, and have worshipped it, and have sacrificed thereunto, and said, These be thy gods, O Israel, which have brought thee up out of the land of Egypt. (Exodus 32:8)
A few weeks previously the people had entered into a solemn covenant with God and pledged themselves to obey Him (chs. 19:8; 24:3). Now that covenant was broken (PP 320). Having “no root” in themselves when temptation came, the people fell quickly into sin (see Matt. 13:20, 21). Many of them, specially those of the “mixed multitude,” could not resist their old idolatrous practices (see 2 Peter 2:22). The word “stiffnecked” conveys the idea of perversity, as with a horse that stiffens its neck when the driver pulls the rein right or left, refusing to go the way it should.