שמות לז:ט מדרש: Midrash Tanchuma

The cherubim were placed directly opposite each other, as it is said: With their faces one to another (ibid. 37:9). This corresponds to the Throne of Glory, which was directly opposite the two cherubim. Each one was directly opposite, as it is said: Out of Zion, the perfection of beauty, God hath shined forth (Ps. 50:2).