The ungratefulness of the Children of Israel when they disbelieved and forsook the worship of Allah for the golden calf 20:86-91
20:86 With great anger and sorrow, Moses returned to his nation. 'My nation,' he said, 'did your Lord not make you a fine promise? Did the time of the covenant seem long to you? Or did you desire that the anger of your Lord should fall upon you so that you failed in your coming to my appointment?'
20:87 They replied, 'We have not failed in our promise to you through our choosing. We were laden with fardels, even the ornaments of the nation, and threw them just as the Samaritan had thrown them (into the fire),