Question : Someone told me that the one who prays 4 rakah sunnah before Jumu^ah prayer is not following Prophet Muhammad, is that correct?
Answer : The scholars differed in this matter, and both the Shafi3iy and Hanafi scholars said that there is a sunnah prayer before the Friday prayer. The Maliki scholars and some Hanbalis said that there is no such sunnah. They all have their proofs, and they are all possibly correct and possibly wrong. It is a matter of what they understood as most likely, and not about certainty. The evidences that made the Hanafis and Shaafi^is say that there is a sunnah are, among other things:
1. Ibn Mas3uud used to order his followers to pray 4 raka^aat before Jumu^ah. The fact that he ordered them indicates that he considered it more than a mere nafl practise. This is why the scholars of Kuufah held this view, as they descend from his school. Is he not following the Prophet also? This accusation reminds me of Ali's words to one person who was rebuking him for delaying Asr prayer (within its time of course). Ali responded "This dog is teaching me the sunnah!"
2. There are several weak hadiths (such as one related by Ibn Maajah) that make up a "hasan" hadith as a group supported by the fact that the Jumu^ah prayer is in the place of Thuhr, so just like Thuhr it has 4 rak^aat before it.
3. Zain al-Deen Al-^Iraaqi mentions in his book Tarh-Al-Tathriib that the hadith of Ibn Maajah, which is weak, has been related through an acceptable chain by al-Khula3i in his fawaa'id.
Finally, it should be kept in mind that what remains today of hadith collections and biographies of hadith relators is nothing like what was in the hands of the salaf. One should never accuse them of "leaving hadith" or the like, because they would never do so intentionally, and because their knowledge was much greater than anyone in this day and age.