Ancient Israel was repeatedly tested and found wanting. Few receive the faithful warnings given them of God. Darkness and unbelief do not decrease as we near the time of the second advent of Christ. Truth becomes less and less palatable to the carnally minded; their hearts are slow to believe and tardy to repent. The servants of God might well become discouraged, were it not for the continual evidences their Master gives them of His wisdom and assistance. Long has the Lord borne with His people. He has forgiven their wanderings and waited for them to give Him room in their hearts; but false ideas, jealousy, and distrust have crowded Him out. 4T 155.1 Few who are professedly of Israel, and whose minds have been enlightened by the revelations of divine wisdom, dare to come boldly forward, as did Caleb, and stand firmly for God and the right. Because those whom the Lord has chosen to conduct His work will not be turned from the course of integrity to gratify the selfish and unconsecrated,…
"So we see that they could not enter in because of unbelief."
Both passages discuss the unbelief of the Israelites and its consequences. Hebrews 3:19 states they couldn't enter due to unbelief, while EGW elaborates on the nature of their unbelief and its parallels to her contemporary context.
"Thousands would accept the truth if they could do so without denying self, but this class would never build up the cause of God. These would never march out valiantly against the enemy,—the world, the love of self, and the lusts of the flesh,—trusting their divine Leader to give them the victory. The church needs faithful Calebs and Joshuas, who are ready to accept eternal life on God's simple condition of obedience. Our churches are suffering for laborers. The world is our field. Missionaries are wanted in cities and villages that are more certainly bound by idolatry than are the pagans of the East, who have never seen the light of truth. The true missionary spirit has deserted the churches that make so exalted a profession; their hearts are no longer aglow with love for souls and a desire to lead them into the fold of Christ. We want earnest workers. Are there none to respond to the cry that goes up from every quarter: “Come over ...and help us”? 4T 155.4"
"Then said Jesus unto his disciples, If any man will come after me, let him deny himself, and take up his cross, and follow me."
EGW directly references the principle of self-denial for following God, which is the core message of Matthew 16:24. She applies this principle to the need for dedicated workers in the church.