Okla. Stat. tit. 58, § 58-486: Holder of mortgage may purchase land

At any sale under order of the district court, of lands upon

which there is a mortgage or lien, the holder thereof may become the

purchaser, and his receipt for the amount due him from the proceeds

of the sale is a payment pro tanto. If the amount for which he

purchased the property is insufficient to defray the expenses and

discharge his mortgage or lien, he must pay to the judge an amount

sufficient to pay such expenses.