In the third aliyah, Moshe rebukes the Jews for the times they angered G-d in the desert and how they were a difficult people. He specifically reviews the details of the sin of the golden calf. Just 40 days after the Ten Commandments were given at mount Sinai, the Jews made an idol. G-d wanted to destroy them, but Moshe went back up the mountain to seek atonement for the Jews and it was granted on the tenth of Tishrei, the day we observe as Yom Kippur, our everlasting Day of Atonement.