How do we know that a saved person cannot be lost?

The doctrine of eternal security is supported by multiple scriptural truths. Firstly, God's eternal purpose guarantees the salvation of His elect (Jeremiah 32:38-40). Secondly, the promises made by Christ, such as in John 6:37, affirm that all who come to Him will not be cast out. Moreover, the blood of Christ acts as a perfect ransom, ensuring that those for whom it was shed are eternally secure (1 John 1:7). These foundational truths collectively affirm that true believers, who are genuinely saved, will persevere in faith until the end.