Jesus proclaimed that he would not lose one of those that God gave him (see John 10:28). But how does God keep His elect? By means of His Word (John 10:27).
God elects, and those He elects will persevere until the end, and the means by which God causes that perseverance is both His commanding Word, and ears to hear that command. Those who are His sheep will hear His warnings about falling away, and take evasive action, and not fall away. A great example of this tactic of God is found in Hebrew 2, verse 1:
Therefore we must pay much closer attention to what we have heard, lest we drift away from it.
And why? The Old Testament saints had their Word delivered by angelic messengers, through prophets (1:14). But now in the new covenant, we have an even clearer mode of communication from God: Jesus Himself (1:1-4). Before, He spoke in the language of prophets and angels, but now He speaks in the language of a Son, who is the exact imprint of the nature of God (1:3).
It’s an argument from the lesser to the greater: if the Old Testament saints were held accountable by God for how they listened, how much more us, we who possess an even clearer message?