זוהר שמות — דף יט ע”א

At the birth of Levi, the celestial angels broke into song. The tribe of Levi was chosen and sanctified to stand in the watches of song corresponding to the heavens. Solomon composed the Song of Songs from that supernal song. Amram returned to his wife discreetly, and on the day he took part in the Shekhinah he merited to beget Moses.