A: In the times of the Bible there really wasn’t pornography like we have now. Back then they obviously didn’t have photographs, the Internet, or television. There was adultery in those times, and according to the Bible (Mt. 5:27-29) pornography falls under adultery. In these three verses Jesus says: “You have heard that it was said, ‘You shall not commit adultery.’ But I say to you everyone who looks at a woman with lust has already committed adultery with her in his heart.” When Jesus says “lust” he means thoughts of immoral behavior or behaving immorally.
So if you like someone, or feel attracted to somebody, that’s not adultery. It becomes the sin of adultery when you lust over someone or an image. In the Bible, Saint Paul says to the Corinthians in 6:18-20, “Flee from sexual immorality. All other sins a man commits are outside his body, but he who sins sexually sins against his own body. Do you not know that your body is the temple of the Holy Spirit, who is in you, whom you have received from God? You are not your own; you were bought at a price. Therefore honor God with your body.” That pretty much reinstates what I said before about lust but also tells us that respecting our bodies is respecting the Lord.
There might be more about adultery and subjects related to it in the Bible but those verses seem the most clear about teachings on pornography. So, those quotes from Jesus and Paul basically address your question. In few sentences, Jesus and Paul tell us pornography is adultery. Adultery goes against the law of God.