The sealing is God's stamp of guarantee we will be in Heaven no matter how badly a Christians succumbs to evil thinking.
And you also were included in Christ when you heard the message of truth, the gospel of your salvation.
When you believed, you were marked in him with a seal, the promised Holy Spirit, who is a deposit guaranteeing our inheritance until the redemption of those who are God’s possession—to the praise of his glory." Ephesians 1:13-14
That means?
Arminians and Calvinists will be playing musical chairs together in Heaven!
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