Only the firstlings of the beasts
These are excepted from being sanctified, or set apart for sacred uses, for a very good reason, suggested in the next clause:
which should be the Lord's firstling, no man shall sanctify it;
it being what he has a claim upon, and ordered to be sanctified to him by a law previous to this, ( Exodus 13:2 ) ; wherefore to sanctify such a creature, would be to sanctify what was his before; not merely in a general sense, in which all creatures are his, but in a special sense, having in a peculiar manner required it as his; and therefore to sanctify, or vow to him, what was his before, must be trifling with him, and mocking of him:
whether [it be] ox, or sheep;
the firstlings of either of them:
it [is] the Lord's;
which he has claimed as his own special and peculiar property, antecedent to any vow of its owner.