Leviticus 27:30 (KJV)

And all thy estimations shall be according to the shekel of the sanctuary: twenty gerahs shall be the shekel.

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 LORD's.

And if it be of an unclean beast, then he shall redeem it according to thine estimation, and shall add a fifth part of it thereto: or if it be not redeemed, then it shall be sold according to thy estimation.

Notwithstanding no devoted thing, that a man shall devote unto the LORD of all that he hath, both of man and beast, and of the field of his possession, shall be sold or redeemed: every devoted thing is most holy unto the LORD.

None devoted, which shall be devoted of men, shall be redeemed; but shall surely be put to death.

And if a man will at all redeem ought of his tithes, he shall add thereto the fifth part thereof.

And concerning the tithe of the herd, or of the flock, even of whatsoever passeth under the rod, the tenth shall be holy unto the LORD.

He shall not search whether it be good or bad, neither shall he change it: and if he change it at all, then both it and the change thereof shall be holy; it shall not be redeemed.

These are the commandments, which the LORD commanded Moses for the children of Israel in mount Sinai.