“Blessed are the clean of heart, for they will see God.” (Matthew 5:8)

“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.” (Matthew 5:27)
“It is also said, ‘Whoever divorces his wife must give her a bill of divorce.’ But I say to you, ‘Whoever divorces his wife (unless the marriage is unlawful) causes her to commit adultery, and whoever marries a divorced woman commits adultery.” (Matthew 5:31-32)

Jesus did not use too much words to condemn the sins of un-cleanliness. This is because the sin has its root in selfishness, without true love. Thus, Jesus always emphasizes on the importance of love. “Do to others whatever you would have them do to you. This is the law and the prophets.” (Matthew 7:12)

“I give you a new commandment: love one another. As I have loved you, so you also should love one another.” (John 13:34)

Following is a very good example:

“Then the scribes and the Pharisees brought a woman who had been caught in adultery and made her stand in the middle. They said to him, ‘Teacher, this woman was caught in the very act of adultery. Now in the law, Moses commanded us to stone such women. So what do you say?’ … Jesus said to them, ‘Let the one among you who is without sin be the first to throw a stone at her.’… Jesus straightened up and said to her, ‘Woman, where are they? Has no one condemned you?’ She replied, ‘No one, sir.’ Then Jesus said, ‘Neither do I condemn you. Go, and from now on do not sin any more.’” “From now on, do not sin any more!” is the advice Jesus gives to every sinner. It is also the advice Jesus gives, in particular to every one of us who knows Him and were chosen by Him.