Okla. Stat. tit. 84, § 84-8: Claim under heir against devisee - Probate proceedings

The rights of a purchaser or encumbrancer of real property in

good faith, and for value, derived from any person claiming the same

by succession, are not impaired by any devise made by the decedent

from whom succession is claimed, unless the instrument containing

such devise has been duly admitted to probate by a court of this

state having jurisdiction to administer upon the estate of the

decedent within two (2) years after the death of the decedent, or

unless within one (1) year after the death of the decedent a

petition to admit said will to probate has been duly filed in the

court of this state having jurisdiction to admit said will to

probate and the proceedings have been pursued by the petitioner with

diligence.