Numbers 9:11 Kabbalah

בַּחֹ֨דֶשׁ הַשֵּׁנִ֜י בְּאַרְבָּעָ֨ה עָשָׂ֥ר י֛וֹם בֵּ֥ין הָעַרְבַּ֖יִם יַעֲשׂ֣וּ אֹת֑וֹ עַל־מַצּ֥וֹת וּמְרֹרִ֖ים יֹאכְלֻֽהוּ׃

in the second month on the fourteenth day at dusk they shall keep it; they shall eat it with unleavened bread and bitter herbs;

Read kabbalistic (mystical) interpretation of Numbers 9:11: and classical mystical sources.