Adam Clarke on Numbers 15:30

But the soul that doeth aught presumptuously - Bold daring acts of transgression against the fullest evidence, and in despite of the Divine authority, admitted of no atonement; the person was to be cut off - to be excluded from God's people, and from all their privileges and blessings.

Probably the presumption mentioned here implied an utter contempt of the word and authority of God, springing from an idolatrous or atheistical mind. In such a case all repentance was precluded, because of the denial of the word and being of God. It is probably a case similar to that mentioned Heb 6:4-8 (note); Heb 10:26-31 (note); on which passages see the notes.