Does the Qur'an say it is haram to have sex before marriage?
I need a reference in the Qur'an to be sure that before marriage sex is haram or forbidden. What is the punishment of having before marriage sex?
You and me ought to pay attention that haram is haram. And Zina is considered as a haram act from the viewpoint of both Sunni and Shia. On the other hand, it cannot be declined by saying that the Quran has not talked about the Hormah of Zina before marriage. Because it has named it explicitly as a forbidden practice in the Quran and it has not named it as a halal act before marriage. Therefore we must obey the holy Quran if we really believe in it as the book of Allah which has presented by the Prophet. Otherwise, it is something else if we'd like to try to justify our sin as an act which we are interested in. Consequently, we must be honest and fair regarding halal and haram pratices...
In truth, the best reference is the verse(s) of the holy Quran that I suggest you to read some of them. Such as:
وَالَّذِينَ لَا يَدْعُونَ مَعَ اللَّـهِ إِلَـٰهًا آخَرَ وَلَا يَقْتُلُونَ النَّفْسَ الَّتِي حَرَّمَ اللَّـهُ إِلَّا بِالْحَقِّ وَلَا يَزْنُونَ ۚ وَمَن يَفْعَلْ ذَٰلِكَ يَلْقَ أَثَامًا ﴿٦٨﴾ يُضَاعَفْ لَهُ الْعَذَابُ يَوْمَ الْقِيَامَةِ وَيَخْلُدْ فِيهِ مُهَانًا ﴿٦٩
And those who do not invoke with Allah another deity or kill the soul which Allah has forbidden [to be killed], except by right, and do not commit unlawful sexual intercourse. And whoever should do that will meet a penalty. (68) Multiplied for him is the punishment on the Day of Resurrection, and he will abide therein humiliated - (69)
ولا تقربوا الزنا انه كان فاحشة و ساء سبيلا
And do not approach unlawful sexual intercourse. Indeed, it is ever an immorality and is evil as a way. (32) اسراء /
Eventually, I'd like to make it more clear by giving you an example. For example, somebody is interested in the pork and wine (although it is clear that wine and pork are haram, cos are harmful...), then s/he ought not to ask I will eat them because the holy Quran has not mentioned that it is haram if you eat them before marriage! fairly, will you accept this question?!
Or as another example, doctors say eating poison will kill people. So, will you eat poison by saying "I eat it, because doctors have not said that it will kill people who are before the age puberty or marriage?!
Consequently I assume you agree with me. Then obey the orders of Allah till He give you more valuable in this world and in Jannah. on the other hand we should avoid commiting some sins (although we really interested in) if we'd like to go to the heaven, otherwise ...