Concise Bible Dictionary:

This is referred to in scripture under various aspects.

From Anstey’s Doctrinal Definitions:

Death always involves separation in some way or another. It is used in Scripture in at least seven different ways. The context dictates which aspect is in view. They are:
The reader will note that each aspect of death involves separation of some kind. It is sobering to think that sin is the cause of every one of these aspects of death! Truly, “the wages of sin is death” (Rom. 6:2323For the wages of sin is death; but the gift of God is eternal life through Jesus Christ our Lord. (Romans 6:23)).
The Bible tells us that there are only two states in which a person can die (physically). It is either in “in the Lord (Rev. 14:1313And I heard a voice from heaven saying unto me, Write, Blessed are the dead which die in the Lord from henceforth: Yea, saith the Spirit, that they may rest from their labors; and their works do follow them. (Revelation 14:13)) or “in your sins” (John 8:2424I said therefore unto you, that ye shall die in your sins: for if ye believe not that I am he, ye shall die in your sins. (John 8:24)). To die in one’s sins is to pass out of this world without having had our sins put away before God judicially by the work of Christ on the cross. The person who dies in that awful condition will be responsible to pay the price of his sins under the righteous judgment of God in a lost eternity. To die in the Lord is to die being safe and secure from all judgment under the shelter of the blood of Christ, God’s Son (John 5:2424Verily, verily, I say unto you, He that heareth my word, and believeth on him that sent me, hath everlasting life, and shall not come into condemnation; but is passed from death unto life. (John 5:24); 1 John 1:77But if we walk in the light, as he is in the light, we have fellowship one with another, and the blood of Jesus Christ his Son cleanseth us from all sin. (1 John 1:7)). The death of a believer is “precious in the sight of the LORD” (Psa. 116:1515Precious in the sight of the Lord is the death of his saints. (Psalm 116:15)), whereas the death of an unbeliever is something that God has “no pleasure” in, because it means that that person will be eternally lost (Ezek. 33:1111Say unto them, As I live, saith the Lord God, I have no pleasure in the death of the wicked; but that the wicked turn from his way and live: turn ye, turn ye from your evil ways; for why will ye die, O house of Israel? (Ezekiel 33:11); 2 Peter 3:99The Lord is not slack concerning his promise, as some men count slackness; but is longsuffering to us-ward, not willing that any should perish, but that all should come to repentance. (2 Peter 3:9)).

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