Why is fornication or adultery considered a sin in Christianity?

Why is pornography a sin? Who am I hurting?- Part 1

What Is The Coptic Orthodox Church’s View On Sex and Sexuality? - Part 1

Journey to the Kingdom: Hope

From The Cross To Resurrection

STUCK AND ENSLAVED - Slavery to Sonship Part 1

The Life - Part 1

2010 Holy Week St. Mark DC - Part 5 (Eve of Wednesday)

2008 Holy Week St. Mark DC - Part 6 (Holy Thursday)