וַיַּעֲשׂ֣וּ אֶת־הַפֶּ֡סַח בָּרִאשׁ֡וֹן בְּאַרְבָּעָה֩ עָשָׂ֨ר י֥וֹם לַחֹ֛דֶשׁ בֵּ֥ין הָעַרְבַּ֖יִם בְּמִדְבַּ֣ר סִינָ֑י כְּ֠כֹל אֲשֶׁ֨ר צִוָּ֤ה יְהוָה֙ אֶת־מֹשֶׁ֔ה כֵּ֥ן עָשׂ֖וּ בְּנֵ֥י יִשְׂרָאֵֽל׃
And they kept the passover in the first month, on the fourteenth day of the month, at dusk, in the wilderness of Sinai; according to all that the LORD commanded Moses, so did the children of Israel.
Read Kabbalistic (mystical) interpretations of Numbers 9:5: Zohar and classical Jewish mystical sources, free online.