וְיָצַ֣קְתָּ לּ֗וֹ אַרְבַּע֙ טַבְּעֹ֣ת זָהָ֔ב וְנָ֣תַתָּ֔ה עַ֖ל אַרְבַּ֣ע פַּעֲמֹתָ֑יו וּשְׁתֵּ֣י טַבָּעֹ֗ת עַל־צַלְעוֹ֙ הָֽאֶחָ֔ת וּשְׁתֵּי֙ טַבָּעֹ֔ת עַל־צַלְע֖וֹ הַשֵּׁנִֽית׃
And thou shalt cast four rings of gold for it, and put them in the four feet thereof; and two rings shall be on the one side of it, and two rings on the other side of it.
Read kabbalistic (mystical) interpretation of Exodus 25:12: and classical mystical sources.