It doesn't say it that specific way. But it does say it clearly.
Eph 1:13,
14
13 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,
14 who is a deposit guaranteeing our inheritance until the redemption of those who are God’s possession—to the praise of his glory.
So, we see here that the Holy Spirit who seals the one "having believed", is a DEPOSIT GUARANTEEING what? Our inheritance.
When? Until the redemption of God's possession.
So, since we are "marked IN HIM with the Holy Spirit, that is what marks us as God's possession.
Please explain what a GUARANTEED DEPOSIT means, and then explain what "our inheritance" means.
When that is done, you'll see eternal security clearly.