The lajnah were asked:

Question:

“Some Imams start offering Tarawih (special supererogatory night Prayer in Ramadan) before the sighting of the new crescent of Ramadan is declared. What is the ruling on this practice?”

Answer:

“This should not be done, as Tarawih Prayer should offered during the month of Ramadan. Thus, no one should offer it until the government declares the sighting of the new crescent of Ramadan.” [Reference]

Mentioned by

Faisal Ibn Abdul Qaadir Ibn Hassan
Abu Sulaymaan