How do we know salvation requires both the blood and the washing of the Spirit?

Salvation encompasses both the sacrificial blood of Christ, which justifies and forgives sin, and the washing of regeneration by the Holy Spirit, which cleanses believers from the filth of their nature. John 3:5 explains that one must be born again by water and the Spirit, emphasizing the necessity of both elements in the salvation process. The blood of Jesus atones for sin, while the washing of the Holy Spirit creates a new nature that is holy and acceptable to God, thereby ensuring complete salvation.