"Like the waters of the Flood the fires of the great day declare God's verdict that the wicked are incurable. They have no disposition to submit to divine authority. Their will has been exercised in revolt; and when life is ended, it is too late to turn the current of their thoughts in the opposite direction, too late to turn from transgression to obedience, from hatred to love. GC 543.1"
"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 idea of a point of no return, where repentance and change are no longer possible. Hebrews speaks of those who have tasted of the heavenly gift and fallen away, while EGW speaks of the wicked whose will has been exercised in revolt and cannot be changed after death.
"In sparing the life of Cain the murderer, God gave the world an example of what would be the result of permitting the sinner to live to continue a course of unbridled iniquity. Through the influence of Cain's teaching and example, multitudes of his descendants were led into sin, until “the wickedness of man was great in the earth” and “every imagination of the thoughts of his heart was only evil continually.” “The earth also was corrupt before God, and the earth was filled with violence.” Genesis 6:5, 11 . GC 543.2"
"And God saw that the wickedness of man was great in the earth, and that every imagination of the thoughts of his heart was only evil continually."
EGW directly quotes Genesis 6:5 to support her argument about the consequences of sparing Cain's life and the resulting increase in wickedness.
"The earth also was corrupt before God, and the earth was filled with violence."
EGW directly quotes Genesis 6:11 to support her argument about the consequences of sparing Cain's life and the resulting corruption and violence on earth.
"In mercy to the world, God blotted out its wicked inhabitants in Noah's time. In mercy He destroyed the corrupt dwellers in Sodom. Through the deceptive power of Satan the workers of iniquity obtain sympathy and admiration, and are thus constantly leading others to rebellion. It was so in Cain's and in Noah's day, and in the time of Abraham and Lot; it is so in our time. It is in mercy to the universe that God will finally destroy the rejecters of His grace. GC 543.3"
"And God saw that the wickedness of man was great in the earth, and that every imagination of the thoughts of his heart was only evil continually."
EGW directly references the wickedness of man in Noah's time as a parallel to her own time, echoing the sentiment expressed in Genesis 6:5. The verse provides the biblical basis for her statement about the extent of wickedness.
"Then the Lord rained upon Sodom and upon Gomorrah brimstone and fire from the Lord out of heaven;"
EGW mentions the destruction of Sodom as an act of God's mercy, which is directly related to the event described in Genesis 19:24. The verse provides the specific action that EGW references.