"Let ministers and people remember that gospel truth hardens when it does not save. The rejection of light leaves men captives, bound about by chains of darkness and unbelief. “The soul that refuses to listen to the invitations of mercy from day to day can soon listen to the most urgent appeals without an emotion stirring his soul. As laborers with God we need more fervent piety and less self-exaltation. The more self is exalted, the more will faith in the Testimonies of the Spirit of God be lessened.... Those who trust wholly in themselves will see less and less of God in the Testimonies of His Spirit.” [ Testimonies for the Church 5:134 (1882) .] 5T 681.3"
"For it is impossible for those who were once enlightened, and have tasted of the heavenly gift, and were made partakers of the Holy Ghost, And have tasted the good word of God, and the powers of the world to come, If they shall fall away, to renew them again unto repentance; seeing they crucify to themselves the Son of God afresh, and put him to an open shame."
Both passages discuss the hardening of the heart and the consequences of rejecting light/grace. Hebrews 6:4-6 describes the impossibility of renewal after falling away, while EGW describes the soul becoming numb to appeals. The theme of spiritual decline due to rejection of truth connects them.