Ash-Shaykh Bin Baaz, rahimahullah, was asked the following question
Is it permissible to offer the Jumu`ah (Friday) Prayer before noontime?
It is permissible to offer it before noontime. However, it is preferable to offer it after noontime in order to avoid the disagreement of scholars over this issue. The majority of scholars state that the Jumu`ah Prayer has to be offered after noontime. Some other scholars have made it permissible to offer the Jumu`ah Prayer before noontime as there are many authentic Hadiths narrated to that effect.
If one offers it a short time before noontime, it will be valid. However, one should offer it after noontime in order to be in line with all Hadiths narrated from the Prophet (peace be upon him) in this regard and in order to make it easy for Muslims to go to the Masjid (mosque) all at the same time. This is the preponderant opinion.