What is the significance of the word "Chata'ah Gedolah"?
Oznayim la'Torah: Initially he thought that the sin of the Eigel was a relatively small one and whrn he showed them the Luchos they would immediately retract and do Teshuvah. Only mow, when he saw the extent of Yisrael's sin, Hashem's statement (in Pasuk 8) "Saru Maher min ha'Derech asher Tzivisim" hit him with full force. 1
Erchin, 15b: The Torah writes "Chata'ah Gedolah" in connection and "Lashon Medaberes Gedolos" - in Tehilim, 12:4; To teach us that the sin of someone who speaks Lashon ha'Ra is as great as that of someone who serves Avodah Zarah. 2
Why did Moshe add the word "Vaya'asu lahem Elohei Zahav"?
Rashi (citing B'rachos, 32a): He was placing the blame of the Golden Calf with Hashem for having provided Yisrael with so much gold. 1
Oznayim la'Torah: In order to stress the fact that gold - a craving for material pleasures, was the root of the sin of the Golden Calf. 2
Yerushalmi Yoma, 7:3: It is because they made the god (the Eigel) out of gold that the Kohen Gadol is not permittted to enter the Kodesh Kodashim on Yom Kipur 3 with the Bigdei Kehunah that contain gold - because 'Ein Kategor Na'aseh Saneigor' ('A prosecutor cannot become a defense counsel').
Rashi (citing B'rachos, Ibid.): If a king feeds his son food and drink, adorns him, ties a purse full of money around his neck and places him outside a brothel, can the son then be blamed for sinning?
Based on the words "ve'Di Zahav" in Devarim, 1:1.
See Torah Temimah, note 42.