“For this is God’s will: that you become holy, that you keep away from sexual immorality, that each of you know how to possess his own body in holiness and honor, not in lustful passion like the Gentiles who do not know God” (1 Thessalonians 4:3-5 NET).
In the original language of this passage, the phrase “sexual immorality” is derived from the word porneia, a word that serves as the basis for our modern-day word “pornography.” In general, “sexual immorality” encompasses any type of sexual expression that goes beyond God’s design for human sexual relationships. Jesus defined that standard in the New Testament Gospel of Mark…
“…at the beginning of creation God ‘made them male and female.’ ‘For this reason a man will leave his father and mother and be united to his wife, and the two will become one flesh.’ So they are no longer two, but one. Therefore what God has joined together, let man not separate'” (Mark 10:6-9 NIV).
So Jesus drew our attention to God’s initiative in establishing the marriage institution. He also provided us with the appropriate parameters for sexual relationships by way of these quotations from Genesis 1:27 and Genesis 2:24. Those parameters involve a God-initiated, monogamous relationship between a genetic male and a genetic female who have joined in a Biblically lawful marriage as husband and wife. Physical relationships that fall outside these Scriptural parameters come under the general definition of “sexual immorality.”
Jesus expanded that definition to include internal expressions of sexual immorality as well…
“You have heard that it was said to those of old, ‘You shall not commit adultery.’ But I say to you that whoever looks at a woman to lust for her has already committed adultery with her in his heart” (Matthew 5:27-28).
Two commentators also identify the similarities between first-century views of sexuality and modern-day attitudes toward sexual expression…
“Paul gave these commands to a first-century Roman culture that was marked by sexual immorality. At this time in the Roman Empire, chastity and sexual purity were almost unknown virtues. Nevertheless, Christians were to take their standards of sexual morality from God and not from the culture.” (1)
“Immorality was common among heathen peoples. It may be that, in his report of the general steadfastness of the Thessalonian Christians, Timothy had mentioned some cases of moral laxness which occasioned this exhortation.” (2)
In light of this, we can say that Paul the Apostle’s letter to the Thessalonians entered a culture that embraced sexual promiscuity. Therefore, this counsel would have been poorly received by many within the culture of that time, just as it is also rejected among many today.
(1) David Guzik, 1 Thessalonians 4 – Confidence In The Coming Of Jesus 2. (3-6a) The command to be sexually pure. © Copyright – Enduring Word https://enduringword.com/bible-commentary/1-thessalonians-4/
(2) Henry H. Halley, Halley’s Bible Handbook, 1 Thessalonians Chapter 4. Immorality. Love. The Lord’s Coming [pg. 627] Copyright © 2000, 2007 by Halley’s Bible Handbook, Inc.