After the sin of the golden calf, Moshe appeals to Hashem to spare the people and forgive them. Hashem Himself teaches Moshe a special prayer that appeals to G-d's attribute of mercy and can be invoked at times of crisis. This tefila, known as "the Attributes of Mercy," or "Yud-Gimel Midot," is familiar to us, because we say it extensively during the 10 Days of Repentance each year (it also is said each morning in nusach S'fard). The prayer utilizes different names for Hashem, each of which is a unique aspect of Hashem's "mode" of forgiveness. It describes G-d as One who forgives both before and after we sin; who helps us avoid temptation to sin; who is patient with our mistakes; who recognizes our weaknesses and takes them into account; who is quick and loyal to reward us when we do overcome sin; who forgives us when we let our angry overcome us, and even when we want to commit sins to anger G-d; who strikes our sins from the record after we repent. He also "saves" merits from our ancestors in previous generations and applies them to us when we need saving.
Beit Midrash Torah Portion and Tanach Ki Tisa