Here is the law concerning real estates dedicated to the service of God by a singular vow.

I.Suppose a man, in his zeal for the honour of God, should sanctify his house to God (Lev 27:14), the house must be valued by the priest, and the money got by the sale of it was to be converted to the use of the sanctuary, which by degrees came to be greatly enriched with dedicated things, Kg1 15:15. But, if the owner be inclined to redeem it himself, he must not have it so cheap as another, but must add a fifth part to the price, for he should have considered before he had vowed it, Lev 27:15. To him that was necessitous God would abate the estimation (Lev 27:8); but to him that was fickle and humoursome, and whose second thoughts inclined more to the world and his secular interest than his first, God would rise in the price. Blessed be God, there is a way of sanctifying our houses to be holy unto the Lord, without either selling them or buying them. If we and our houses serve the Lord, if religion rule in them, and we put away iniquity far from them, and have a church in our house, holiness to the Lord is written upon it, it is his, and he will dwell with us in it.

II.Suppose a man should sanctify some part of his land to the Lord, giving it to pious uses, then a difference must be made between land that came to the donor by descent and that which came by purchase, and accordingly the case altered.

1.If it was the inheritance of his fathers, here called the field of his possession, which pertained to his family from the first division of Canaan, he might not give it all, no, not to the sanctuary; God would not admit such a degree of zeal as ruined a man's family. But he might sanctify or dedicate only some part of it, Lev 27:16. And in that case, (1.) The land was to be valued (as our countrymen commonly compute land) by so many measures' sowing of barley. So much land as would take a homer, or chomer, of barley, which contained ten ephahs, Eze 45:11 (not, as some have here mistaken it, an omer, which was but a tenth part of an ephah, Exo 16:36), was valued at fifty shekels, a moderate price (Lev 27:16), and that if it were sanctified immediately from the year of jubilee, Lev 27:17. But, if some years after, there was to be a discount accordingly, even of that price, Lev 27:18. And, (2.) When the value was fixed, the donor might, if he pleased, redeem it for sixty shekels the homer's sowing, which was with the addition of a fifth part: the money then went to the sanctuary, and the land reverted to him that had sanctified it, Lev 27:19. But if he would not redeem it, and the priest sold it to another, then at the year of jubilee, beyond which the sale could not go, the land came to the priests, and was theirs for ever, Lev 27:20, Lev 27:21. Note, What is given to the Lord ought not to be given with a power of revocation; what is devoted to the Lord must be his for ever, by a perpetual covenant.

2.If the land was his own purchase, and came not to him from his ancestors, then not the land itself, but the value of it was to be given to the priests for pious uses, Lev 27:22, Lev 27:24. It was supposed that those who, by the blessing of God, had grown so rich as to become purchasers would think themselves obliged in gratitude to sanctify some part of their purchase, at least (and here they are not limited, but they might, if they pleased, sanctify the whole), to the service of God. For we ought to give as God prospers us, Co1 16:2. Purchasers are in a special manner bound to be charitable. Now, forasmuch as purchased lands were by a former law to return at the year of jubilee to the family from which they were purchased, God would not have that law and the intentions of it defeated by making the lands corban, a gift, Mar 7:11. But it was to be computed how much the land was worth for so many years as were from the vow to the jubilee; for only so long it was his own, and God hates robbery for burnt-offerings. We can never acceptably serve God with that of which we have wronged our neighbour. And so much money he was to give for the present, and keep the land in his own hands till the year of jubilee, when it was to return free of all encumbrances, even that of its being dedicated to him of whom it was bought. The value of the shekel by which all these estimations were to be made is here ascertained (Lev 27:25); it shall be twenty gerahs, and every gerah was sixteen barley-corns. This was fixed before (Exo 30:13); and, whereas there had been some alterations, it is again fixed in the laws of Ezekiel's visionary temple (Eze 45:12), to denote that the gospel should reduce things to their ancient standard.

As a field devoted - It is חרם cherem, a thing so devoted to God as never more to be capable of being redeemed. See on Lev 27:29 (note).

And all thy estimation shall be according to the shekel of the sanctuary,.... The shekel kept in the sanctuary, which was the standard of all shekels; not that there was a shekel in the sanctuary different from the common one; for every shekel ought to have been as that, of the full weight and worth of it; and the estimation was to be according to such a shekel, and the money paid in such, even in full weight:

twenty gerahs shall be the shekel; which the Targum of Jonathan calls "meahs" or "oboli", one of which was about three halfpence of our money, scarce so much, and weighed near eleven grains, as Bishop Cumberland (i) has calculated: see Eze 45:12.

(i) Of Scripture Weights and Measures, ch. 4. p. 111.

if a man shall sanctify unto the Lord some aprt of a field of his possession, &c.--In the case of acquired property in land, if not redeemed, it returned to the donor at the Jubilee; whereas the part of a hereditary estate, which had been vowed, did not revert to the owner, but remained attached in perpetuity to the sanctuary. The reason for this remarkable difference was to lay every man under an obligation to redeem the property, or stimulate his nearest kinsman to do it, in order to prevent a patrimonial inheritance going out from any family in Israel.