وَلَا يَتَنَفَّلُ فِي الْمُصَلَّى قَبْلَ صَلَاةِ الْعِيدِ.
Translation: One should not perform voluntary prayer in the Eid prayer ground before the Eid prayer.
The musalla is the communal Eid prayer ground. Avoiding pre-Eid voluntary prayer there belongs to the Hanafi arrangement; other schools distinguish some mosque and outdoor-prayer-ground cases.