The following is an excerpt from The MacArthur New Testament Commentary on John 10.

and I give eternal life to them, and they will never perish; and no one will snatch them out of My hand. (10:28)Repeating what He said in His discourse on the Good Shepherd (see the exposition of vv. 3–5 in the previous chapter of this volume), Jesus said, “My sheep hear My voice, and I know them, and they follow Me.” The elect will heed Christ’s call to salvation and continue in faith and obedience to eternal glory (cf. Rom. 8:29–30).

The Lord continued by articulating the wonderful truth that those who are His sheep need never fear being lost. “I give eternal life to them,” Jesus declared, “and they will never perish; and no one will snatch them out of My hand. 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.” Nowhere in Scripture is there a stronger affirmation of the absolute eternal security of all true Christians. Jesus plainly taught that the security of the believer in salvation does not depend on human effort, but is grounded in the gracious, sovereign election, promise, and power of God.

Christ’s words reveal seven realities that bind every true Christian forever to God. First, believers are His sheep, and it is the duty of the Good Shepherd to protect His flock. “This is the will of Him who sent Me,” Jesus said, “that of all that He has given Me I lose nothing, but raise it up on the last day” (6:39). To insist that a true Christian can somehow be lost is to deny the truth of that statement. It is also to defame the character of the Lord Jesus Christ—making Him out to be an incompetent shepherd, unable to hold on to those entrusted to Him by the Father.

Second, Christ’s sheep hear only His voice and follow only Him. Since they will not listen to or follow a stranger (10:5), they could not possibly wander away from Him and be eternally lost.

Third, Christ’s sheep have eternal life. To speak of eternal life ending is a contradiction in terms.

Fourth, Christ gives eternal life to His sheep. Since they did nothing to earn it, they can do nothing to lose it.

Fifth, Christ promised that His sheep will never perish. Were even one to do so, it would make Him a liar.

Sixth, no one—not false shepherds (the thieves and robbers of v. 1), or false prophets (symbolized by the wolf of v. 12), nor even the Devil himself—is powerful enough to snatch Christ’s sheep out of His hand.

Finally, Christ’s sheep are held not only in His hand, but also in the hand of the Father, who is greater than all; and thus no one is able to snatch them out of His hand either. Infinitely secure, the believer’s “life is hidden with Christ in God” (Col. 3:3).

The Father and the Son jointly guarantee the eternal security of believers because, as Jesus declared, “I and the Father are one” (the Greek word one is neuter, not masculine; it speaks of “one substance,” not “one person”). Thus their unity of purpose and action in safeguarding believers is undergirded by their unity of nature and essence. The whole matter of security is summarized in our Lord’s own words in John 6:39–40:   This is the will of Him who sent Me, that of all that He has given Me I lose nothing, but raise it up on the last day. 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.Incensed by what they accurately and unmistakably perceived as another blasphemous claim to deity by Jesus, the Jews, self-righteously exploding in a fit of passion, picked up stones again to stone Him—the fourth time in John’s gospel that they had attempted to kill Him (5:16–18; 7:1; 8:59). Though the Romans had withheld the right of capital punishment from the Jews (18:31), this angry lynch mob was ready to take matters into its own hands.
MacArthur, J. (2006). The MacArthur New Testament commentary : John 1-11 (441–443). Chicago: Moody Press.