שָׁלֹ֥שׁ פְּעָמִ֖ים בַּשָּׁנָ֑ה יֵרָאֶה֙ כָּל־זְכ֣וּרְךָ֔ אֶל־פְּנֵ֖י הָאָדֹ֥ן ׀ יְהוָֽה׃
Three times in the year all thy males shall appear before the Lord GOD.
Read kabbalistic (mystical) interpretation of Exodus 23:17: and classical mystical sources.