According to official FIFA news on June 18th, Brazilian referee Raphael Claus will officiate the FIFA World Cup group stage match between Spain and Saudi Arabia. 

Spain vs. Saudi Arabia Referee Team

Referee: Raphael Claus (Brazil)

Assistant Referee: Danilo Manis(Brazil)

Assistant Referee: Rodrigo Figueiredo(Brazil)

Fourth Official: Andrés Rojas(Colombia)

Reserve Assistant Referee: Alexander Guzmán(Colombia)