כִּי֩ נְתֻנִ֨ים נְתֻנִ֥ים הֵ֙מָּה֙ לִ֔י מִתּ֖וֹךְ בְּנֵ֣י יִשְׂרָאֵ֑ל תַּחַת֩ פִּטְרַ֨ת כָּל־רֶ֜חֶם בְּכ֥וֹר כֹּל֙ מִבְּנֵ֣י יִשְׂרָאֵ֔ל לָקַ֥חְתִּי אֹתָ֖ם לִֽי׃
For they are wholly given unto Me from among the children of Israel; instead of all that openeth the womb, even the first-born of all the children of Israel, have I taken them unto Me.
Read halakhic rulings (Jewish law) on Numbers 8:16: and classical halakhic sources.