“Discourses on humility give occasion for pride to the boastful, and for humility to the humble.”
Pascal points to a self-referential danger: even learning or speaking about humility can become another stage for vanity unless a person is willing to examine the motives behind the performance.
Source details
The Thoughts of Blaise Pascal, C. Kegan Paul translation, Project Gutenberg #46921. The next sentence extends the paradox by observing how difficult it is to speak humbly about humility.