Harden hearts in unbelief

1. Alma 33: 21
     21 O my brethren, if ye could be healed by merely casting about your eyes that ye might be healed, would ye not behold quickly, or would ye rather harden your hearts in unbelief, and be slothful, that ye would not cast about your eyes, that ye might perish?
2. D&C 20: 15
     15 But those who harden their hearts in unbelief, and reject it, it shall turn to their own condemnation—