All are to be chaste…both the married and unmarried…
vatican.va/archive/catechism/p3s2c2a6.htm#II
A couple a of examples from Scripture (RSV)
You have heard that it was said, `You shall not commit adultery.’
But I say to you that every one who looks at a woman lustfully has already committed adultery with her in his heart. If your right eye causes you to sin, pluck it out and throw it away; it is better that you lose one of your members than that your whole body be thrown into hell. And if your right hand causes you to sin, cut it off and throw it away; it is better that you lose one of your members than that your whole body go into hell. (Matt 5:27-30)
Paul to the Romans (6)
What shall we say then? Are we to continue in sin that grace may abound?
[2] By no means! How can we who died to sin still live in it?
[3] Do you not know that all of us who have been baptized into Christ Jesus were baptized into his death?
[4] We were buried therefore with him by baptism into death, so that as Christ was raised from the dead by the glory of the Father, we too might walk in newness of life.
[5]
For if we have been united with him in a death like his, we shall certainly be united with him in a resurrection like his.
[6] We know that our old self was crucified with him so that the sinful body might be destroyed, and we might no longer be enslaved to sin.
[7] For he who has died is freed from sin.
[8] But if we have died with Christ, we believe that we shall also live with him.
[9] For we know that Christ being raised from the dead will never die again; death no longer has dominion over him.
[10] The death he died he died to sin, once for all, but the life he lives he lives to God.
[11] So you also must consider yourselves dead to sin and alive to God in Christ Jesus.
[12]
Let not sin therefore reign in your mortal bodies, to make you obey their passions.
[13] Do not yield your members to sin as instruments of wickedness, but yield yourselves to God as men who have been brought from death to life, and your members to God as instruments of righteousness.
[14] For sin will have no dominion over you, since you are not under law but under grace.
[15]
What then? Are we to sin because we are not under law but under grace? By no means!
[16] Do you not know that if you yield yourselves to any one as obedient slaves, you are slaves of the one whom you obey, either of sin, which leads to death, or of obedience, which leads to righteousness?
[17] But thanks be to God, that you who were once slaves of sin have become obedient from the heart to the standard of teaching to which you were committed,
[18] and, having been set free from sin, have become slaves of righteousness.
[19] I am speaking in human terms, because of your natural limitations. For just as you once yielded your members to impurity and to greater and greater iniquity, so now yield your members to righteousness for sanctification.
[20]
When you were slaves of sin, you were free in regard to righteousness.
[21] But then what return did you get from the things of which you are now ashamed? The end of those things is death.
[22] But now that you have been set free from sin and have become slaves of God, the return you get is sanctification and its end, eternal life.
[23] For the wages of sin is death, but the free gift of God is eternal life in Christ Jesus our Lord.
Paul to the Ephesians
But fornication and all impurity or covetousness must not even be named among you, as is fitting among saints.
[4] Let there be no filthiness, nor silly talk, nor levity, which are not fitting; but instead let there be thanksgiving.
[5] Be sure of this, that no fornicator or impure man, or one who is covetous (that is, an idolater), has any inheritance in the kingdom of Christ and of God.
[6] Let no one deceive you with empty words, for it is because of these things that the wrath of God comes upon the sons of disobedience.
[7] Therefore do not associate with them,
[8] for once you were darkness, but now you are light in the Lord; walk as children of light
[9] (for the fruit of light is found in all that is good and right and true),
[10] and try to learn what is pleasing to the Lord.
[11] Take no part in the unfruitful works of darkness, but instead expose them.
