“The gospel is full of inconceivably extravagant promises from our Father. He has given these promises to provide His children with the full assurance of His freely given, irrevocable love, and they are grounded in His steadfast, immovable, unchangeable faithfulness.
What God promises He will infallibly bring to pass. And all the promises the Father makes are bound up inextricably in Jesus Christ, in whom they are fulfilled and completed: ‘For no matter how many promises God has made, they are ‘Yes’ in Christ’ (2 Cor. 1:20, niv1984).
In order to bring to fruition all that He has promised us, God joins us indissolubly to the One in whom all the promises are contained, fulfilled, and secured. It is only in Christ that we benefit from any of God’s lavish pledges.
Thus, the assurance believers have that God will infallibly save them, and that they will never cease to be saved, is rooted in their being joined to the Savior. The Father gives us to the Son, and it is the Father’s will that the Son save us to the uttermost:
‘And this is the will of Him who sent me, that I should lose nothing of all that He has given me, but raise it up on the last day. For this is the will of my Father, that everyone who looks on the Son and believes in Him should have eternal life, and I will raise him up on the last day’ ( John 6:39–40).
Our separation from Jesus Christ would mean nothing less than the failure of the Son to accomplish the Father’s will. Once joined to Christ, believers will never be separated from Him.
This is not because our grasp on Christ is so strong, but because His grip on us is unbreakable. We are not only perfectly and eternally preserved in Christ because His grasp is insuperable, but, should we need even greater assurance, Jesus tells us that His hold on us is undergirded by the invincible grasp of His Father:
‘I give [my sheep] eternal life, and they will never perish, and no one will snatch them out of my hand. My Father, who has given them to me, is greater than all, and no one is able to snatch them out of the Father’s hand. I and the Father are one’ ( John 10:28–30).
The Son and the Father have a common and mutually re-enforcing grasp on those who belong to them. Indeed, we can say more: our preservation in Christ is anchored in the personal relations and purposes of the Father, Son, and Spirit.
The Father gives us to His Son through His Spirit or, alternatively, the Spirit joins us to the Son, and through the Son to the Father (John 14:16–20). Only a breach in the common unity and will of the triune Godhead could sever us from Jesus Christ.”
–Marcus Peter Johnson, One With Christ: An Evangelical Theology of Salvation (Wheaton: Crossway, 2013), 173-174.