How do we know the doctrine of Christ is true?

According to 1 John 4:2-3, the true Spirit of God is recognized by the confession that 'Jesus Christ is come in the flesh.' This vital doctrine asserts both the divinity and humanity of Jesus, which are foundational to the Christian faith. A denial of Christ's human nature not only undermines His incarnation but also distorts the gospel message that salvation is found in His perfect obedience and sacrifice. This standard for testing spirits highlights the importance of adhering to biblical doctrines, as failing to do so aligns one with the spirit of antichrist, which denies the core tenets of the Christian faith.