“power over the spirit.” The Hebrew word translated “spirit” is ruach (#07307 רוּחַ), and it is the common word for “spirit,” but it has many meanings. It refers to the spirit life in man, thus “life” or sometimes “breath;” the attitudes and emotions of man; God, who is the Spirit; angels; demons; the wind; and more. [For much more on the use of ruach, see Appendix 6, “Usages of ‘Spirit’”].
Many commentators think that in this verse, ruach refers to the wind, and that may be possible, but in light of the second phrase about the day of death, it seems to be more connected to our life, making “spirit” a good translation (cp. ASV, ESV, KJV, NLT, Rotherham, and cp. NAB). The fact is that any person reading the Hebrew text itself would read ruach and immediately see all the possibilities, including both our life and the wind, neither of which we can retain or restrain. For all the bravado about how powerful we humans are, the actual fact is that we don’t know that much and don’t have much power. God, on the other hand, knows everything available to know and created the whole universe from nothing. No wonder Jesus told us to trust God (John 14:1), and no wonder Jeremiah said we would be cursed if we trusted in humans and relied on human power (Jer. 17:5).
“that war.” The war between life and death. The Hebrew is literally, “the war,” but “that war” is nuanced from the context (cp. Fox, Ecclesiastes).
“rescue its owners.” There is an inherent deception in witchcraft and evil in general, and that is that the person who is doing the evil “owns” it, that is, they have a measure of control over the demons they are using or the evil they are doing. The person doing evil may feel that they are in control of their situation and what they are doing will get them what they want—power, prestige, money, sex, etc.—but in the end they will find that aging and death happens to everyone. They will discover that the evil they have been involved with will not be able to rescue them from death no matter how much power and/or control they thought it gave them in life. After the Fall, God decreed that humans would age and die, and after death comes the Day of Judgment (Heb. 9:27), and wickedness cannot rescue an evil person from death and the Lake of Fire and everlasting death that comes after Judgment Day. In fact, far from delivering the wicked, Psalm 34:21 even says that wickedness will kill the wicked.
[For information on annihilation in the Lake of Fire, see Appendix 5, “Annihilation in the Lake of Fire].