I Kings 6:17 Kabbalah

וְאַרְבָּעִ֥ים בָּאַמָּ֖ה הָיָ֣ה הַבָּ֑יִת ה֖וּא הַהֵיכָ֥ל לִפְנָֽי׃

And the house, that is, the temple before [the Sanctuary], was forty cubits long.

Read kabbalistic (mystical) interpretation of I Kings 6:17: and classical mystical sources.