God's commandments forbid adultery. It's in the Bible, Exodus 20:14, NIV. "You shall not commit adultery."
To leave your spouse for another person may be legal, but it is adultery in God's eyes. It's in the Bible, Luke 16:18, NIV. "Anyone who divorces his wife and marries another woman commits adultery, and the man who marries a divorced woman commits adultery."
Lust is a form of adultery. It's in the Bible, Matthew 5:27-28, NIV. "You have heard that it was said, 'Do not commit adultery.' But I tell you that anyone who looks at a woman lustfully has already committed adultery with her in his heart."
How did Jesus relate to a woman caught in the act of adultery? It's in the Bible, John 8:10-11, TLB. "Then Jesus stood up again and said to her, 'Where are your accusers? Didn't even one of them condemn you?' "No sir," she said. And Jesus said, 'Neither do I. Go and sin no more.'"
It is God's will that we should avoid sexual immorality. It's in the Bible, I Thessalonians 4:3, NIV. "It is God's will that you should be sanctified: that you should avoid sexual immorality."
The path of adultery will leave you with ugly wounds and scars. It's in the Bible, Proverbs 6:28-29, "Can one walk on hot coals, and his feet not be seared? So is he who goes in to his neighbor’s wife; whoever touches her shall not be innocent."
What warning does the Bible give for committing adultery? It's in the Bible, Proverbs 6:32:33, NKJV. "Whoever commits adultery with a woman lacks understanding; He who does so destroys his own soul. Wounds and dishonor he will get, and his reproach will not be wiped away."
What is spiritual adultery in the Bible? Worshipping other gods, idols, and in ways God hasn't called for. It's in the Bible, Ezekiel 23:37, NKJV. "For they have committed adultery, and blood is on their hands. They have committed adultery with their idols, and even sacrificed their sons whom they bore to Me, passing them through the fire, to devour them"