זוהר שמות — דף רנ ע”א

The wheel over the forty appointees reaches the chamber of runners, where Hashmalim angels carry golden shields to protect Israel from other nations. Twelve wheels revolve in this palace, called Seraphim in two colors — white and red, mercy and judgment — and watch over those who suffer oppression. When prayer begins to ascend, these angels accompany it through all the heavens and palaces up to the supreme gate. Happy are the righteous who know how to properly arrange their prayer.