Douglass states that both the kindness of his mistress and the bitter opposition of his master were a "benefit"in helping him learn to read. What evidence from the text
supports this idea?

The evidence from the text that supports the idea that bitter opposition of his master and kindness of his mistress were beneficial for him is when Mr. Auld forbade his wife from teaching lessons to Douglass as it will make him unfit to be a slave. In other words, Mr. Auld knew if Douglass would receive education than he would find his way to freedom.

Explanation:

'Narrative of the Life of Frederick Douglass' is an autobiographical account of Frederick Douglass, a former slave, who walked on the path from slavery to freedom by educating himself.

In his account he shares one incidence, which benefitted him and made him aware of the path of freedom from slavery through education. When Douglass was sold as a slave to Mr. Auld, his wife, Mrs. Auld, in her kindness began giving Douglass lessons of alphabets. But, one day, Mr Auld came to know about these lessons that his wife was giving to Douglass, and he forbade her instantly from giving any lessons to Douglass. Mr. Auld stated that if he would receive any sort of education then he would become unfit to be slave.

This instance of Mr. Auld's bitter opposition towards the kindness of Mrs. Auld in giving lessons to Douglass became beneficial for him because after this incidence he came to know that his pathway towards freedom from slavery is education.

Textual Evidence:

"Just at this point of my progress, Mr. Auld found out what was going on, and at once forbade Mrs. Auld to instruct me further, telling her, among other things, that it was unlawful, as well as unsafe, to teach a slave to read. To use his own words, further, he said, “If you give a ni-g-ger an inch, he will take an ell. A ni-g-ger should know nothing but to obey his master—to do as he is told to do. Learning would spoil the best ni-g-ger in the world."

Further, Douglass writes that these words of his master sank deep in his heart and brought awakening to him.

it was the first amendment