When thou passest through the waters, I will be with thee; and through the rivers, they shall not overflow thee: when thou walkest through the fire, thou shalt not be burned; neither shall the flame kindle upon thee." -- Isaiah 43:1-2.
"All that the Father giveth me shall come to me; and him that cometh to me I will in no wise cast out.
For I came down from heaven, not to do mine own will, but the will of him that sent me.
And this is the Father's will which hath sent me, that of all which he hath given me I should lose nothing, but should raise it up again at the last day.
And this is the will of him that sent me, that every one which seeth the Son, and believeth on him, may have everlasting life: and I will raise him up at the last day." -- John 6:37-40.
Faith in Jesus Christ is our ticket to heaven. Everyone who has a ticket will get in.
But we didn't buy the ticket ourselves. We didn't print the ticket, steal the ticket or earn the ticket.
God alone, according to His mercy from before the foundation of the world, gave us our ticket, paid for by the blood of His only Son, Jesus Christ, who will not lose any whom the Father has given Him.
Sounds pretty indelible to me.
No scalping tickets, either. They're not for sale, at any price. ONLY the original ticket holders will get in. As it has been said another way: God doesn't have grandchildren.
Faith in Christ is the evidence of God's choosing, not the cause of it.