What was the purpose of the gag rule?

The gagging of anti-slavery petitions by Congress occurred from 1835 to 1844. Pro-slavery forces had prevented any discussion of slavery in Congress, so anti-slavery forces, starting in about 1831, had submitted petitions for the abolition of slavery, believing that since there was a right to petition the government as guaranteed in the First Amendment of the Constitution, such petitions, and thus slavery itself, would have to be discussed.