Deuteronomy 15:19

All the firstling males.... thou shalt sanctify — i.e., recognise them as the property of Jehovah by not using them for ordinary purposes. In Leviticus 27:26 we read, “No man shall sanctify it” — i.e., shall make it the subject of a special vow or dedication, because it already belongs to Jehovah. This is the only interpretation consistent with the context in Leviticus; for Deuteronomy 27 deals entirely with “voluntary” offerings, which are in a sense outside the Law. (See Notes at the commencement of Deuteronomy 28:29).