כַּאֲשֶׁ֛ר צִוָּ֥ה יְהוָ֖ה אֶת־מֹשֶׁ֑ה וַֽיִּפְקְדֵ֖ם בְּמִדְבַּ֥ר סִינָֽי׃ (פ)
As the LORD commanded Moses, so did he number them in the wilderness of Sinai.
Read kabbalistic (mystical) interpretation of Numbers 1:19: and classical mystical sources.