Paul explains that the law of Moses is no longer in effect. While this is true, the timeless principles behind the law reflect the character of God. (See: [[rc://en/tw/dict/bible/kt/lawofmoses]])
Scripture commonly uses marriage as a metaphor. Here Paul uses it to describe how the church relates to the law of Moses and now to Christ. (See: [[rc://en/ta/man/translate/figs-metaphor]])
This is a complex issue. "Flesh" is possibly a metaphor for our sinful nature. Paul is not teaching that our physical bodies are sinful. Paul appears to be teaching that as long as Christians are alive ("in the flesh"), we will continue to sin. But our new nature will be fighting against our old nature. (See: [[rc://en/tw/dict/bible/kt/flesh]] and [[rc://en/tw/dict/bible/kt/sin]])
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