Quaint John Bunyan used an illustration which is as helpful as it is simple in showing how secure the believer is in Christ.
He takes the simile of Isa. 22:23, 2423And I will fasten him as a nail in a sure place; and he shall be for a glorious throne to his father's house. 24And they shall hang upon him all the glory of his father's house, the offspring and the issue, all vessels of small quantity, from the vessels of cups, even to all the vessels of flagons. (Isaiah 22:23‑24) where Christ is seen as "a nail in a sure place," and of which it is said, "They shall hang upon Him all the glory of His Father's house, the offspring and the issue, all vessels of small quantity, from the vessels of cups, even to all the vessels of flagons.”
Everything for God's glory depends upon Christ and His glorious work, and everything for the sinner's salvation and for the believer's security depends upon Him and His glorious work as well.
Bunyan says that there is a nail driven securely into a strong wall, and on that nail hangs a great iron cauldron in perfect safety. That vessel weighs perhaps half a hundred weight. Beside it on the same nail hangs a little tin cup. Both are in perfect safety. They both depend on the same support, but the little tin cup shivers and shakes and wonders if the nail can hold it up. Then he supposes the cauldron saying, "You silly little tin cup, the nail holds me safely, and it can hold a thousand like you.”
The work of redemption of our Lord Jesus Christ upholds all the glory of God: His majesty, His honor, His faithfulness. All is maintained by Christ, and His work holds up safely every believer too. Trust Him fully. "He is able also to save them to the uttermost that come unto God by Him." Heb. 7:2525Wherefore he is able also to save them to the uttermost that come unto God by him, seeing he ever liveth to make intercession for them. (Hebrews 7:25).