לִבְנֵ֣י יִשְׂרָאֵ֗ל וְלַגֵּ֤ר וְלַתּוֹשָׁב֙ בְּתוֹכָ֔ם תִּהְיֶ֛ינָה שֵׁשׁ־הֶעָרִ֥ים הָאֵ֖לֶּה לְמִקְלָ֑ט לָנ֣וּס שָׁ֔מָּה כָּל־מַכֵּה־נֶ֖פֶשׁ בִּשְׁגָגָֽה׃
For the children of Israel, and for the stranger and for the settler among them, shall these six cities be for refuge, that every one that killeth any person through error may flee thither.
Read kabbalistic (mystical) interpretation of Numbers 35:15: and classical mystical sources.