Numbers 13:4 Kabbalah

וְאֵ֖לֶּה שְׁמוֹתָ֑ם לְמַטֵּ֣ה רְאוּבֵ֔ן שַׁמּ֖וּעַ בֶּן־זַכּֽוּר׃

And these were their names: of the tribe of Reuben, Shammua the son of Zaccur.

Read kabbalistic (mystical) interpretation of Numbers 13:4: and classical mystical sources.