Here is the backdrop: Though the most blatant idolaters in the nation had already been put to death by the sword for their sin of idolatry with the golden calf, Moses knew that the nation as a whole was still guilty before God. The fact is, God had made a covenant with the nation as a whole, and the nation as a whole now bore collective guilt for this breach of the covenant (see Joshua 7).
Moses, therefore, wanted to make things right by seeking to make atonement (literally, "cover" the sin) for the people (Exodus 32:20). Moses seems to have assumed that the penalty for their sin would be death, as is often threatened in the law (28:43). Moses informed God that if He did not forgive forgive the people (removing the death penalty), he wanted to have his name removed from the book God had written (32:22).
......it is clear from this passage that God rejected Moses's offer and promised to punish the sinners themselves by premature death (Exodus 32:33,34). This indicates that no human being can atone for the sins of another. The prophets often spoke of individual responsibility for sins (Jeremiah 31:29, 30; Ezekiel 18; 33:10-20)....
Clearly, then, this passage provides no support for any so-called "treasury of merit" from which those in need can draw by indulgences. Such an idea is completely foreign to the context."
Ron Rhodes, Reasoning from the Scriptures with Catholics, p. 160-162