John 10:28 - I give them eternal life, and they shall never perish; no one will snatch them out of my hand.
The first phrase "I give them eternal life" identifies recipients of the gift of eternal life (Rom 6:23).
The second phrase "they shall never perish" is the promise of Jesus. So, the direct result of being a recipient of eternal life is that they shall never perish.
Note that Jesus added no contingencies, conditions, or requirements beyond simply being a recipient of eternal life for the promise of never perishing.
This promise clarifies any misunderstanding of John 5:24 where some claim that only those who "currently" believe have eternal life and will not be condemned.
That claim is untrue because the Greek present tense doesn't mean "on-going action" or "continuous action out into the future".
It only means "right now", or "currently", or "presently".
So, John 5:24 and John 10:28 are saying the exact same thing. When one believes, they are given eternal life. And will never perish, which is based on simply being the recipient of eternal life.
These verses teach that we are saved by believing in Jesus Christ.
Luke 8:12 "Those beside the road are those who have heard; then the devil comes and takes away the word from their heart, so that they will not believe and be saved.
Acts 4:12 "And there is salvation in no one else; for there is no other name under heaven that has been given among men by which we must be saved."
Acts 11:14 and he will speak words to you by which you will be saved, you and all your household.'
Acts 16:31- They said, “Believe in the Lord Jesus, and you will be saved, you and your household."
Rom 10:9, 10
9 that if you confess with your mouth Jesus as Lord, and believe in your heart that God raised Him from the dead, you will be saved; 10 for with the heart a person believes, resulting in righteousness, and with the mouth he confesses, resulting in salvation.
Rom 1:16 For I am not ashamed of the gospel, for it is the power of God for salvation to everyone who believes, to the Jew first and also to the Greek.
Eph 2:8 For by grace you have been saved through faith; and that not of yourselves, it is the gift of God;
2 Tim 3:15 and that from childhood you have known the sacred writings which are able to give you the wisdom that leads to salvation through faith which is in Christ Jesus.
1 Peter 1:5 who are protected by the power of God through faith for a salvation ready to be revealed in the last time.
1 Peter 1:9 obtaining as the outcome of your faith the salvation of your souls.
These verses teach that receiving eternal life is based on believing in Christ:
John 3:15-16
15 so that whoever believes will in Him have eternal life. 16 "For God so loved the world, that He gave His only begotten Son, that whoever believes in Him shall not perish, but have eternal life.
John 3:36 "He who believes in the Son has eternal life; but he who does not obey the Son will not see life, but the wrath of God abides on him."
John 5:24 "Truly, truly, I say to you, he who hears My word, and believes Him who sent Me, has eternal life, and does not come into judgment, but has passed out of death into life.
John 6:40 "For this is the will of My Father, that everyone who beholds the Son and believes in Him will have eternal life, and I Myself will raise him up on the last day."
John 6:47 "Truly, truly, I say to you, he who believes has eternal life.
Rom 6:23 For the wages of sin is death, but the free gift of God is eternal life in Christ Jesus our Lord
1 Tim 1:16 Yet for this reason I found mercy, so that in me as the foremost, Jesus Christ might demonstrate His perfect patience as an example for those who would believe in Him for eternal life.
Gal 3:22 But the Scripture has shut up everyone under sin, so that the promise by faith in Jesus Christ might be given to those who believe.
1 John 5:13 - These things I have written to you who believe in the name of the Son of God, so that you may know that you have eternal life.
We know that those who believe in Christ are given etenral life. We know that those who are given eternal life are recipients of eternal life. And we know that recipients will never perish.
This is eternal security.