What Harry Potter book during occlumency lessons did Harry see snape's past?

In "Harry Potter and the Order of the Phoenix," during the Occlumency lessons with Professor Snape, Harry inadvertently glimpses Snape's past. This occurs in chapter 24, titled "Occlumency," where Harry experiences memories of Snape's childhood and his time at Hogwarts, particularly interactions with his childhood rival, James Potter. These revelations provide deeper insight into Snape's character and motivations.