The Messenger of Allah ﷺ used to wear his ring with the stone facing the inside of his palm.
أن رسول الله ﷺ كان يجعل فصه مما يلي كفه.
Muslim narrated it in the Book of Dress and Adornment (2094, 62) through several routes from Talha bin Yahya Zuraqi, from Yunus, from Ibn Shihab, from Anas bin Malik, who related it.As for his saying, "He would place its stone toward the inside of his palm," the scholars said, the Prophet ﷺ did not give any instruction about this, so it is permissible to place the stone on the inside of the palm or on the outside of it, and the early generations practiced both ways. They said, the inside is better, in emulation of the Prophet ﷺ, and because it better protects the stone and keeps it safer, and it is further removed from vanity and self-admiration. This is what Nawawi said.