The salvation of sinners, determined by God in old eternity, was no easy matter. To create the world and all that is in it required only the spoken word of God. "For He spake, and it was done; He commanded, and it stood fast." But to rescue chosen sinners required these two things.
1. The Lord of glory had to humble Himself to be made under the law, to live by that law and then to become "obedient unto death, even the death of the cross" (Philippians 2:8) in order to redeem His people. There was this matter of the indebtedness of sinners to divine justice that had to be taken care of. Christ died for us in order to redeem us from the righteous demands of a holy law that required death for sin. As our Substitute, the Son of God endured the infinite wrath of God due our sins. There was no other way the Lord of glory could be just and justify the ungodly. "For He hath made Him to be sin for us, Who knew no sin, that we might be made the righteousness of God" (2 Corinthians 5:21). His resurrection and ascension back to glory are evidences that He successfully accomplished the great work of redemption assigned to Him.
2. The Holy Spirit of God must come in life-giving power to spiritually dead sinners. Such is the inability and lifelessness of sinners that none will repent of their dead works and turn to Christ the Lord in living faith apart from the regenerating power of God the Spirit. It is, in fact, just as impossible for a sinner to believe on Christ as it is for him to keep the law. Only the quickening power of God's Spirit can impart life to those who by nature are "dead in trespasses and in sins" (Ephesians 2:1) and only then will the sinner turn to Christ as his only Lord and Savior, the "only Mediator between God and men, the Man Christ Jesus" (1 Timothy 2:5). None can save except Christ, and none will look to Him apart from the new birth, accomplished by the Spirit.