freeinnocentspirit said in post #1:
Is it possible to convert from one Abrahamic Faith to another?
If by "one Abrahamic Faith" you mean Judaism, of course a Jew can convert to Christianity. Even a Jew who has persecuted Christianity can do so, just like the apostle Paul did (Philippians 3:5-14). He came to know how perfectly the Old Testament foretold the death of Jesus Christ for our sins and Christ's rising from the dead on the third day (Acts 26:22-23, 1 Corinthians 15:1-5, Luke 24:44-47).
Christ's death for our sins was foretold in Isaiah 53 (cf. Acts 8:32-35, 1 Peter 2:24). Christ's crucifixion experience was foretold in Psalms 22 (cf. Matthew 27:46, Matthew 27:35). Christ not remaining dead was foretold in Psalms 16:10 (cf. Acts 2:31). Christ rising from the dead on the third day was foretold in Hosea 6:2 (cf. 1 Corinthians 15:4, Luke 24:46, Colossians 2:12). That Christ's New Covenant gospel (Matthew 26:28) would go forth to save both Jews and Gentiles was foretold in Isaiah 49:6 and Isaiah 42:6 (cf. Acts 26:23b, Luke 24:47).
And Christians can know how perfectly the Old Testament shows the deity of Christ. Christ being uncreated, his having existed forever, from everlasting, is shown in Micah 5:2c (cf. John 8:58, Colossians 1:16-17, John 1:1,14). Christ being YHWH the Holy One, from everlasting, is shown in Habakkuk 1:12a (cf. Acts 3:14, Micah 5:2c). Christ being the human/divine Son of God due to his virgin birth is shown in Isaiah 7:14 (cf. Matthew 1:22-25, Luke 1:34-35). Christ being the mighty God is shown in Isaiah 9:6 (cf. Titus 2:13). Christ being YHWH the good shepherd is shown in Psalms 23:1 (cf. John 10:11, Mark 10:18). Christ being YHWH who will set his feet on the Mount of Olives at his return is shown in Zechariah 14:3-4 (cf. Acts 1:11-12). Christ being YHWH the Redeemer who is the first and the last is shown in Isaiah 44:6 (cf. Revelation 2:8, Titus 2:13-14). Christ being YHWH the great I AM is shown in Exodus 3:14 (cf. John 8:58). Christ being one God with God the Father, equal in divinity with God the Father, is shown in Isaiah 45:5-6 and Isaiah 43:10b (cf. John 10:30, John 20:28, Philippians 2:6), for they show that YHWH is the only God, and that he has always been and forever will be the only God.
For some other examples of how Jesus Christ fulfilled Old Testament scriptures at his first coming: Moses foretold of Jesus Christ in Deuteronomy 18:15,18,19 (cf. Acts 3:22-24, Luke 24:44). Jesus fulfilled Zechariah 9:9 in Matthew 21:4-5. Psalms 118:22 was fulfilled at Jesus Christ's first coming (Acts 4:11). Isaiah 9:1-2 was fulfilled in Matthew 4:12-16. Psalms 110:4 is fulfilled by Jesus Christ's high priesthood (Hebrews 6:20). Zechariah 6:11-12 and Zechariah 3:8-9 meant by type that the Christ would be a high priest named "Joshua"/"Jesus" ("Jesus" is simply the Greek form of the Hebrew name "Joshua"); "The Branch" is a title of the Christ (Isaiah 4:2-6, Jeremiah 33:14-17); and where it says "upon one stone shall be seven eyes" (Zechariah 3:9), even this is fulfilled by Jesus, the stone (cf. 1 Peter 2:7), who is at one point symbolically shown as having seven "eyes" (Revelation 5:6).
So it can be known with certainty that Jesus of Nazareth is the Christ (cf. John 20:31), because he perfectly fulfilled the Old Testament scriptures regarding Christ's first coming (Luke 24:44-48). And yet non-Christian Judaism still continues to deny all of this, just as it continues to deny the Trinity, because it lacks understanding of the Old Testament's teachings regarding Christ (2 Corinthians 3:14); just as before Christ came, no one at all could understood these teachings, because they were kept secret by God, hidden from everyone (Romans 16:25-26, cf. Luke 18:34). They were first revealed to the apostles by Christ himself after his resurrection (Luke 24:44-47, Galatians 1:12), and were then recorded in the New Testament.
---
If by "one Abrahamic Faith" you mean Islam, of course a Muslim can convert to Christianity, once he or she realizes that Islam is actually an anti-gospel religion, because, even though it affirms that Jesus is the Christ (e.g. Koran 4:157, Koran 5:17, Koran 5:75), it denies that Jesus Christ is the human/divine Son of God (Koran 9:30, Koran 4:171, Koran 5:72), and it denies that Jesus Christ died on the Cross for our sins (Koran 4:157) and rose from the dead on the third day. In order to be saved, people have to believe the gospel that Jesus Christ is the human/divine Son of God (John 3:16,36, 1 John 2:23), and that Jesus Christ died on the Cross for our sins and rose from the dead on the third day (1 Corinthians 15:1-4, Luke 24:46-47, Matthew 20:19, Matthew 26:28).
The reason why it's necessary to believe these things in order to be saved is because it was only as the human/divine Son of God that Jesus Christ's suffering during his Passion could satisfy God the Father's justice (Isaiah 53:11), which requires an infinite amount of human suffering for sin (Matthew 25:46).
Jesus' suffering during his Passion was sufficient to forgive the sins of everyone (1 John 2:2) because Jesus isn't just a human, but also God (John 1:1,14, John 10:30, John 20:28): his soul is infinite, and so the suffering of his soul (Isaiah 53:11) was infinite in amount (even though it wasn't infinite in duration), and so his suffering could satisfy God the Father's justice (Isaiah 53:11).
Because humans who aren't God have finite souls, for them to suffer an infinite amount for their sins they must suffer over an infinite duration of time (Matthew 25:46, Revelation 14:10-11, Mark 9:46). Every human has sinned (Romans 3:23) except Jesus (Hebrews 4:15b, 2 Corinthians 5:21). But because Jesus suffered for sins (1 Peter 3:18, Isaiah 53:11b) an infinite amount, when the elect believe in Jesus' human/divine sacrifice they can have their past sins forgiven (Romans 3:25-26, Matthew 26:28) while God the Father's justice remains fully satisfied by Jesus' suffering for their sins (Isaiah 53:11).
One thing that can help Muslims understand how Jesus Christ can be God, from everlasting, is for them to consider the Muslim belief regarding the Koran. For Islam says that there was no time when the Koran didn't exist in a spiritual form in heaven, that it has always co-existed with Allah as his word. So all a Muslim needs to do is realize that the Bible says that before Jesus Christ's incarnation, there was no time when he didn't exist in a spiritual form in heaven; he has always co-existed with God the Father as God the Word (John 1:1,14).