Islam has introduced marriage as its answer to the needs of men and women, forbidding all other types of sexual relationship between the two genders, let it be intimate speaking, touching and caressing etc.; all of these can only happen after the marriage formula has been executed. Even a boy and girl who are fiancés and are planning to get married in the future, but haven't actually carried out the marriage formula cannot take lustful pleasures in each other, even if it is only limited to intimate speech.[1]

As for zina or fornication, which means to have intercourse with a person who isn't one’s spouse (either by permanent marriage or mut’ah), it is a great sin in the Quran’s view about which Allah (swt) has said: “Do not approach fornication. It is indeed an indecency and an evil way”[2].[3] There are several conditions for an act to be considered zina (which is the subject for numerous rulings such as hadd, or eternal impermissibility of getting married to that individual which applies in some cases) , one of those being for penetration to take place until the glans has been completely enveloped, and until such hasn’t taken place, it isn't deemed zina, although all forms of sensual relationship between non-mahram men and women are haram and a great sin.[4] In any event, both zina (which is intercourse taking place between a man and woman who aren't married (permanently or via mut’ah) and the other acts that lead to it and are usually done before it are great sins, and the practical difference between the two is that in the former (zina), the Islamic governor or judiciary can carry out the hadd on the fornicating individual (which is a punishment specified in the Quran[5]). On the other hand, if the man and woman haven't committed zina and what they have done are other unchaste acts between each other, they have still sinned and the judiciary can punish them; the punishment’s harshness depending on the greatness of what they have done (this type of punishment is called ta’zir).[6] Nevertheless, the punishment mentioned in the Quran won't apply anymore. If one ever wishes to make up for such a sin, all that is needed is for him/her to be truly penitent about it and to ask for repentance from Allah (swt). Also, if these two individuals ever plan on getting married, the fact that they had engaged in such acts before their marriage won't hinder the validity of their marriage.

For further information, see:

1- Question, 671 (website: 717), The ruling of sexual relationship before marriage contract.

2- Question 1222 (website: 1219), The chatting of boys and girls.

3- Question 695 (website: 743), Temporary marriage, the best solution.

4- Question 1407 (website: 1427), Having a relationship with a non-mahram before marriage.

5- Question 3012 (website: 3273) Zina with a married woman.

6- Question 2569 (website: 2723) The ruling on unchaste acts (Zina and others).