Sa'id bin al-Musayyib (may Allah have mercy on him) saw a man praying more than two rak'ahs after the break of dawn, in which he was performing bowings and prostrations, and he forbade him. The man said: O Abu Muhammad! Will Allah Almighty punish me for praying? Sa'id bin al-Musayyib (may Allah have mercy on him) said: No, but Allah Almighty will certainly punish you for going against the Sunnah.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4445