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.

What belonged to the Lord by law could not be dedicated to Him by a vow, especially the first-born of clean cattle (cf. Exodus 13:1-2). The first-born of unclean animals were to be redeemed according to the valuation of the priest, with the addition of a fifth; and if this was not done, it was to be sold at the estimated value. By this regulation the earlier law, which commanded that an ass should either be redeemed with a sheep or else be put to death (Exodus 13:13; Exodus 34:20), was modified in favour of the revenues of the sanctuary and its servants.

Only the firstling of the beasts, which should be the LORD'S firstling, no man shall sanctify it; whether it be ox, or sheep: it is the {n} LORD'S.

(n) It was the Lord's already.

27:26 No man shall sanctify it - By vow; because it is not his own, but the Lord's already, and therefore to vow such a thing to God is a tacit derogation from, and an usurpation of the Lord's right, and a mocking of God by pretending to give what we cannot withhold from him. Or ox or sheep - Under these two eminent kinds he comprehends all other beasts which might be sacrificed to God, the firstlings whereof could not be redeemed but were to be sacrificed; whereas the firstlings of men were to be redeemed, and therefore were capable of being vowed, as we see, 1Sam 1:11.

firstling of: Heb. firstborn, etc

26, 27. Only the firstling of the beasts-These, in the case of clean beasts, being consecrated to God by a universal and standing law (Ex 13:12; 34:19), could not be devoted; and in that of unclean beasts, were subject to the rule mentioned (Le 27:11, 12).

27:26-33 Things or persons devoted, are distinguished from things or persons that were only sanctified. Devoted things were most holy to the Lord, and could neither be taken back nor applied to other purposes. Whatever productions they had the benefit, God must be honoured with the tenth of, if it could be applied. Thus they acknowledge God to be the Owner of their land, the Giver of its fruits, and themselves to be his tenants, and dependants upon him. Thus they gave him thanks for the plenty they enjoyed, and besought his favour in the continuance of it. We are taught to honour the Lord with our substance.