John 10:27 My sheep hear My voice, and I know them, and they follow Me; 28 and I give eternal life to them, and they will never perish; and no one will snatch them out of My hand. 29 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.…
The only people who don’t believe in once saved always saved are those who believe in a works based salvation. They may want to consider the “filthy rags” perception of their best efforts.